Methods and devices for inhibiting hair growth and related skin treatments

Methods of applying laser light to the skin, and apparatus therefor, include methods for removing hair, for synchronizing hair growth, for stimulating hair growth, for treating Herpes virus, for reducing sweat and body odor, for in situ formation of a chromophore in hair ducts, for reducing light loss at the skin surface, for grafting of hair stem cells, and for removing keloid or hypertrophic scars. The hair removal methods include controlling the proportions of photomechanical and photothermal damage by selection of laser parameters, chromophore particle size and/or pulse duration, with optional dynamic skin cooling. Additional hair removal methods include infiltrating a photoactivated drug into hair ducts and exposing the skin to sunlight or administering an anti-proliferative agent into hair ducts, for example, by encapsulating the anti-proliferative agent in a slow release vehicle. The methods of treating Herpes virus, reducing sweat or body odor, and removing keloid or hypertrophic scars include infiltrating a light-absorbing contaminant into hair ducts or other openings in the skin and illuminating the contaminated skin section. The methods for stimulating hair growth include grafting of cloned auto hair stem cells the hair ducts or administering methionine to a skin section to increase hair growth. Apparatus useful in performing these methods include devices for making a smooth optical boundary between skin and air or for dividing a light beam into a plurality of smaller light beams, and dressings for use before, during and after laser illumination.

TECHNICAL FIELD 
This invention relates to devices and methods for hair removal and skin 
treatments. 
BACKGROUND 
The known techniques of hair removal include electrolysis and various laser 
hair removal techniques and skin treatments. Laser hair removal is 
described in United States patents to Weissman et al., U.S. Pat. No. 
4,388,924; Sutton, U.S. Pat. No. 4,617,926; Mayer, U.S. Pat. No. 
3,538,919; and Zaias, U.S. Pat. No. 5,059,192. 
It is also known to effect long-term inhibition of hair growth by 
infiltrating a light-absorbing contaminant into hair ducts in a skin 
section prior to laser treatment. This technique is described in U.S. Pat. 
Nos. 5,226,907 and 5,425,728 to Tankovich. A contaminant applied topically 
can also be used to facilitate laser skin resurfacing. The contaminant is 
infiltrated beneath the surface layers of the stratum corneum, and then 
the skin surface bearing the contaminant is illuminated so as to remove 
the surface layers of the stratum corneum. This technique is described in 
U.S. Pat. No. 5,423,803 to Tankovich. 
Accordingly, after noting the limitations of the prior art techniques, the 
inventors of the present application have devised new methods and devices 
used in long term prevention of hair growth and other beneficial skin 
treatments. 
SUMMARY 
One embodiment of the invention is a method for inducing hairs in a section 
of skin into synchronized hair growth by applying a shock to hair 
follicles in the section of skin. 
Another embodiment of the invention is a method for increasing the gradient 
of energy loss with depth in skin to assist in forcing contaminant 
particles into spaces in hair ducts and other skin structures. Devices for 
dividing a beam of light directed to a skin surface into a plurality of 
substantially smaller beams are useful for exerting a net downward vector 
on contaminant particles within hair ducts or other skin structures in the 
practice of the invention. 
Another embodiment of the invention is a method for infiltrating a 
contaminant into hair ducts on a section of skin wherein the section of 
skin is covered with an occlusive dressing, such as a hydrogel, for long 
enough to cause spreading of the contaminant into the occluded hair ducts. 
Another embodiment of the invention is a hydrogel dressing wherein an 
active agent beneficial for soothing or protecting irritated or inflamed 
skin is incorporated in a hydrogel matrix. 
Another embodiment of the invention is a composite hydrogel for covering a 
skin surface during laser treatments. The hydrogel is scrimless and 
comprises a film of thermoplastic hydrogel joined along one face with a 
layer of cross-linked hydrogel polymer and a photoindicator that changes 
appearance upon irradiation with a laser beam. 
Another embodiment of the invention is a method for controlling the 
proportions of mechanical and thermal damage caused to tissue surrounding 
hair ducts during hair removal procedures. One portion of the particles in 
a contaminant is selected to be large enough to explode upon illumination, 
and a second portion of particle is selected to be small enough to heat up 
without explosion upon illumination. The mechanical damage is proportional 
to the portion of larger particles and the thermal damage is proportional 
to the smaller portion of particles in the contaminant. 
Another embodiment of the invention is a method for providing any desired 
combination of photothermal and photomechanical damage to tissue 
surrounding hair ducts infiltrated with light absorbing particles. A skin 
section containing the hair ducts is illuminated with a combination of 
long and short pulses of light absorbed by the particles, wherein the long 
pulses avoid explosion of a selected portion of the particles, thereby 
causing photothermal damage, and the short pulses explode or vaporize 
another portion of the particles, thereby causing photomechanical damage. 
In another embodiment of the invention, growth of unwanted hairs in hair 
ducts in a section of skin is obtained by topically applying a 
sunlight-activated photochemical associated with microcarrier particles to 
a section of skin, allowing the microcarrier particles to penetrate into 
hair ducts, and bathing the treated section of skin in sunlight. 
Another embodiment of the invention is a method for inhibiting hair growth 
by applying an anti-proliferative agent to hair growth cells in a skin 
section so as to inhibit hair growth in the skin section. 
In another embodiment of the invention, hair growth cells in hair ducts are 
contacted with a hair growth stimulating amount of methionine to stimulate 
hair growth in a section of skin. 
Another embodiment of the invention is a method for preventing or treating 
outbreaks of a skin lesion due to reactivation of Herpes virus latent in 
hair ducts, wherein a contaminant is infiltrated into the hair ducts and 
the skin is illuminated by a light absorbed by the contaminant with 
consequent destruction of the Herpes virus in the hair ducts. 
Another embodiment of the invention is a method for reducing production of 
sweat and/or odor in which a light-absorbing contaminant is infiltrated 
into spaces in hair ducts adjacent to or within sweat glands, and the skin 
is illuminated with a light so as to transfer heat and kinetic energy from 
the contaminant to the tissue surrounding the sweat glands, thereby 
devitalizing the sweat glands and reducing or eliminating production of 
sweat in the treated skin section. 
Another embodiment of the invention is a method for tailoring the treatment 
regimen and energy level used during laser hair removal treatment to 
accommodate such factors as an individual's hair and skin color, the depth 
of hair follicles at the anatomic location of the site to be treated, and 
any previous history of hair removal treatment. 
Another embodiment of the invention is an improvement in a method for laser 
assisted hair removal wherein skin is irradiated with an illumination beam 
with a square or circular shape no wider than about 8.0 mm at its widest 
point. 
Another embodiment of the invention is a method for in situ formation 
within hair ducts of a metal oxide useful as a light absorbing chromophore 
during laser-assisted skin treatments. 
Another embodiment of the invention is a method for reducing loss of light 
due to scattering and reflection of an incident light beam at a skin 
surface wherein the skin surface is covered with a transparent coating of 
liquid or a transparent device with a smooth upper surface for receiving 
an incident light beam. The covering has a refractive index slightly 
greater than or equal to the refractive index of skin to minimize loss of 
energy from the incident beam. 
Another embodiment of the invention is a method for stimulating hair growth 
in which an individual's healthy undifferentiated papilla and/or bulge 
area stem cells are harvested, cloned, and inoculated interdermally into a 
section of skin to stimulate hair growth therein. 
Another embodiment of the invention is a method for removal of hypertrophic 
or keloid scars wherein a scar is coated with a light absorbing 
contaminant and illuminated with short pulses of light preferentially 
absorbed by the contaminant for a time sufficient to selectively remove 
the scar. 
Another embodiment of the invention is a method for inhibiting hair growth 
by filling hair ducts, from which hairs have optionally been removed, with 
a light guiding fluid, and, using a light well absorbed in blood 
chromophores, illuminating the section of skin containing the hair ducts 
so that at least a portion of the light is directed down the hair ducts by 
the fluid and absorbed in blood vessels that feed hair growth cells. 
Another embodiment of the invention is a method for inhibiting hair growth 
by irradiating hair ducts infiltrated with light-absorbing contaminant 
particles, wherein the surface of a section of skin is precooled to about 
10.degree. C. to -10.degree. C. prior to illumination, and a cooling flux 
is maintained on the surface of the skin section during a single laser 
pulse. The duration of the pulse is sufficient that tissue immediately 
surrounding the base of a hair follicle in the section of skin is 
destroyed by heat transferred from the irradiated contaminant. Meanwhile 
the cooling flux on the skin surface is sufficient that the temperature of 
tissue at a distance of about 1 to 2 hair follicle radii from the hair 
duct wall increases to no more than about 10.degree. C. above body 
temperature during the pulse. At the conclusion of the pulse, the cooling 
flux is terminated, and the surface of the section of skin is allowed to 
return to body temperature before the three-step process is repeated. 
Another embodiment of the invention is a method for activating or retarding 
hair growth wherein a contaminant containing metallic particles is applied 
to a skin section containing hair ducts, infiltrating at least some of the 
particles into follicles in the hair ducts, and applying to the skin 
section electromagnetic radiation having a frequency that is absorbed by 
the metallic particles. Radiation absorbed by the particles is transferred 
to surrounding follicular tissue in the form of heat. Depending on the 
phase of growth, thermal damage to the hair follicles can activate or 
retard hair growth. 
The details of one or more embodiments of the invention are set forth in 
the accompanying drawings and the description below. Other features, 
objects, and advantages of the invention will be apparent from the 
description and drawings, and from the claims.

Like reference numbers and designations in the various drawings indicate 
like elements. 
DETAILED DESCRIPTION 
No. 1: A Method of Pretreatment to Synchronize Hair Growth Prior to Hair 
Removal Procedures 
Individual hairs in any given area of skin surface are not normally 
synchronized at a common point in the hair growth cycle. However, at any 
time some proportion of hairs in a skin section are in the anagen phase of 
the hair growth cycle. Hair stem cells and other follicular tissue are 
believed to be more susceptible to long term damage when they are 
activated, i.e., in the anagen phase of the hair growth cycle. However, 
during the mature anagen phase, the hair follicle is fully extended (to a 
depth of about 3.0 to 5.0 mm), and the distance to the bottom of the 
follicle from the skin surface is about twice that during the telogen 
phase of the hair growth cycle. This combination of circumstances makes 
laser-assisted hair removal difficult, particularly if the method of hair 
removal depends upon topical application of a substance, such as a 
contaminant, that is infiltrated throughout hair ducts to aid in the hair 
removal process. 
This problem is overcome in one aspect of the invention by pretreating a 
skin section to be treated for hair removal so as to synchronize the hairs 
in the late telogen/early anagen phase. During this transition from the 
inactive to the active phases of the hair growth cycle, the hair follicle 
is still weak and shallow (at a depth of from 1.0 to 2.0 mm), yet the hair 
cells responsible for hair growth are just beginning to be activated and 
are, therefore, more susceptible to damage than at other phases of the 
hair growth cycle. FIG. 1 shows a section of human skin with a cross 
section of a hair shaft 33, a hair duct 31, a nerve ending 34, a sweat 
gland 35, a sebaceous gland 38, and arteries 36, veins 37 and papilla 32. 
This aspect of the invention provides a method for synchronizing the hair 
cycle of the hairs in a particular area of skin surface. There are nine 
phases or stages in the hair growth cycle: anagen II, IV, V and VI (growth 
phases), catagen III, V, VI and VII (regressing phases), and telogen 
(resting phase) as shown in FIG. 2. During the telogen phase, the follicle 
shrinks until the bottom of the follicle and the follicle papilla abut the 
bulge area. This process may be assisted by contraction of the hair root 
canal cells (similarly to smooth muscles cells) so as to drag the hair 
papilla to a position nearer the skin surface. Recent work has shown that 
stem cells located in the bulge area are responsible for hair regrowth 
during the anagen phase. At some point during telogen phase, the "normally 
slow cycle," stem cells of the bulge area are transiently activated, 
presumably by signals from the abutting follicular papilla. In response, 
the stem cells, which are responsible for hair regrowth, proliferate, 
shifting the hair into anagen phase. During the anagen phases, the 
follicle again extends to its full length, so that the bulge area of the 
hair duct is located about one-half way down the follicle just below the 
sebaceous gland. It is known to treat hair for hair removal during the 
anagen stage when the rapidly proliferating stem cells are easily damaged. 
However, at anagen stage the stem cells are located at a depth as great as 
3.0 to 5.0 mm below the surface of the skin. 
In one embodiment, the goal is to prepare a section of skin for hair 
removal and/or long-term inhibition of hair growth. It has been discovered 
that once the hairs are synchronized in the telogen/early anagen phase of 
the growth cycle, hair removal can be accomplished with increased 
efficiency by any known method. For example, one method includes 
irradiation of the synchronized follicles with light absorbed either by a 
naturally occurring chromophore in the hair duct, such as melanin, or by 
an externally applied light-absorbing contaminant infiltrated into hair 
follicles. 
The hairs on a section of skin are synchronized in the late telogen/early 
anagen phase by irritating or slightly damaging the hair follicles in a 
section of skin so as to stimulate hairs in the skin section that are in a 
catagen or telogen phase to shift into anagen phase of the hair growth 
cycle. The irritation can be provided by mechanical, thermal, or chemical 
means. Any of these means will increase the flow of blood to the hair 
follicles. The only requirement is that the irritation or damage be 
sufficient to activate the natural repair response to slight damage or 
injury, but not sufficient to cause severe damage such as would cause 
hairs already in the anagen phase to be shifted to an inactive state. 
For example, synchronous growth of human hair can be effected by 
application of a drug, such as Minoxidil, which increases flow of blood to 
the hair follicles, or application of Methionine (for example post waxing) 
to increase proliferation of papilla or matrix cells. Such drugs can be 
introduced into the hair root canal either by direct application or 
delivery in microcapsules. 
Alternatively, mild laser treatment of a skin section containing resting 
hair cells, or irradiation by a flash lamp, can be used to shock anagen 
phase hairs into telogen phase while stimulating the resting cells to 
transition into the anagen phase, thus synchronizing the hair cells in the 
growth cycle. In addition, waxing, plucking, or electrolysis of hair 
follicles can be used to provide the shock necessary to synchronize hair 
growth. The degree of irritation or mild injury administered is that 
sufficient to trigger the natural self-protective repair mechanism that 
shifts hairs to the telogen/early anagen phase without causing severe 
damage to the hair cells in the bulge area of the hair follicle. FIG. 35 
shows a laser system 74 useful for illuminating a skin surface including a 
laser 76, a laser control 78, an articulated arm 80 for delivering a laser 
beam, and pulses of laser light 82 in spaced relation to a section of skin 
12 having a contaminant 14 thereon. 
Following application of the shock or irritant, a period of time is 
required for the phase shift to occur, for example a period of from about 
3 to 25 days. It has been discovered by empirical tests that good results 
can generally be obtained by waiting for a period of about 7 to 21 days 
following administration of a shock or irritant for the hairs in a section 
of skin to substantially synchronize. Therefore, if the treatment to 
synchronize the hairs to telogen/early anagen phase growth is preparatory 
to administering a subsequent hair removal treatment, a period of about 7 
to about 21 days should generally be allowed for the phase shift to occur 
before the subsequent hair removal treatment is undertaken. 
Once hair growth is synchronized in late telogen/early anagen phase, the 
skin surface can be illuminated with short pulses of light at a frequency 
absorbed by a naturally occurring chromophore or externally infiltrated 
contaminant. For example, a ruby laser can be used to irradiate the 
melanin within shortened hair follicles. Methods of hair removal that 
depend for their effect upon the ability to infiltrate a light-absorbing 
contaminant deep into the hair follicle, such as those disclosed in U.S. 
Pat. Nos. 5,226,907 and 5,425,728, are enhanced by use of the invention. 
During the mature anagen period of the hair growth cycle when it is 
easiest to damage stem cells and other follicular tissue involved in hair 
growth, it is hardest to infiltrate the contaminant to the bottom of the 
hair follicle, and thereby ensure destruction of follicular tissue 
throughout the length of the hair duct. Synchronizing hair growth in the 
late telogen/early anagen phase greatly reduces the distance into a hair 
duct that a contaminant needs to be infiltrated. 
When the hair removal treatment to be employed on the synchronized hairs 
utilizes an external contaminant infiltrated into the hair ducts, the 
pretreatment method can incorporate the following steps. First, a 
contaminant, i.e., one containing light absorbing chromophore particles, 
is gently applied to the skin section so that at least a portion of the 
contaminant enters the upper region of the hair follicles. For instance an 
oil or water-based suspension of carbon particles or other chromophore 
particles that absorb light in the near IR region of the spectrum, can be 
employed as the externally applied contaminant. Liposomes can also be used 
to deliver into the hair follicles any chromophore which has a good 
absorption at a laser wavelength that is appropriate for illumination of a 
skin section. Hair papilla and/or matrix cells can also be stained with a 
dye which has good absorption of light, using coherent or non-coherent 
light radiation. A mild concentration of a photosensitizer chemical (e.g., 
one that is activated by laser radiation to produce singlet oxygen) can 
also be administered to a skin section, allowed to become absorbed in hair 
growth cells, and then used to shock the hair follicles. Alternatively, a 
mild solution of a chemical that causes irritation to hair follicles upon 
contact can be administered to synchronously stimulate hair growth. For 
example levulenic acid applied to the skin surface so as to infiltrate 
into hair ducts in a concentration of about 0.002 to about 2 percent by 
volume will cause a mild irritation that will shock hair follicles. 
The skin section can be cleaned using a non-irritating cleaner prior to 
application of the contaminant to remove oil and debris, such as lint and 
loose skin cells. For example, lint and cell debris can be removed from 
the skin section with any type of tape having a light adhesive, such as is 
used for lint removal from fabrics, and the like. Another example of a 
non-irritating cleaner is isopropyl alcohol. The skin section generally 
should not be vigorously brushed or rubbed during cleaning prior to 
administration of the contaminant because irritation will cause sebaceous 
glands in the hair ducts to exude a liquid wax that will obstruct entry of 
a contaminant. 
As one example, the contaminant can be a suspension of carbon particles in 
the size range from about 0.2 to about 0.01 micron (carbon black) or in 
the size range up to about 1 micron. The carbon particles are suspended in 
or mixed with a light oil, such as light mineral oil, NF. Drakeol 13.TM. 
(PennDrake, Los Angeles, Calif.), is a preferred oil for this use. 
When applied to the skin section prior to irradiation, at least a portion 
of the contaminant must enter the upper region of the hair follicles, 
i.e., the mouth of the hair follicles. Generally, merely applying the 
contaminant to the skin surface will cause the particles to infiltrate 
only about 20 microns into the hair follicles. Increased penetration of a 
contaminant containing oil may be obtained by allowing the contaminant to 
rest on the skin section for a period of time sufficient for the opening 
of the hair follicle to become enlarged before the next step is taken. 
This effect is thought to be due to the action of the light oil on the 
skin and hair follicles. Usually, allowing an oil-based contaminant to 
remain on a skin section for a period of about 15 minutes is sufficient to 
enlarge the openings of hair follicles to the fullest extent. 
Next, to shock the hair follicles, the contaminated skin section is 
illuminated with one or two short pulses of light having a frequency 
highly absorbed by the contaminant particles. For example, if the 
contaminant contains carbon particles, a frequency is used that is well 
absorbed in carbon, but relatively transparent to skin, such as is 
provided by a Nd:YAG laser. Additional useful light sources are discussed 
in the Tankovich patents incorporated herein by reference. 
In one embodiment of the invention, it is desirable to explode or fracture 
the contaminant particles in the hair ducts during illumination to drive 
them as far as possible into the depth of the hair follicles. In any 
event, it is necessary to irritate or mildly damage the follicular tissue, 
but only enough to trigger a natural repair mechanism in the follicles, 
causing any follicles in anagen phase to pass out of anagen phase into 
telogen phase. Short pulses of light having a low fluence in the range 
from about 1 to about 2.5 J/cm.sup.2 can be used to avoid transferring 
substantial heat and/or kinetic energy from the chromophore particles to 
the hair follicles or surrounding tissue. Serious damage to the hair 
papilla should be avoided. Therefore, preferably no more energy is 
administered to the hair follicles during the pretreatment process than 
will raise the temperature of the follicle walls more than about 
10.degree. C. to about 20.degree. C. above body temperature during the 
laser pulse. 
During the rest period of about 7 to 21 days following administration of 
the shock, hair cells in anagen phase will cycle through telogen phase 
into early anagen phase, a point in the hair growth cycle referred to 
herein as "late telogen/early anagen phase." However, if too much heat is 
transferred to the hair follicles during the pretreatment, hair growth 
generally will not be synchronized. 
After observing the rest period to allow synchronization of hair growth in 
the "late telogen/early anagen phase," a hair removal procedure can, in 
many cases, be undertaken with the expectation of an increased level of 
success. It has been discovered that when the hair growth cycle has been 
synchronized using the method of this invention, the percentage of hairs 
that are sufficiently devitalized to inhibit regrowth for an extended 
period of time (for example 3 to 6 weeks, or longer) is substantially 
increased. 
Use of a contaminant for shocking the papillae is optional, and is omitted 
if the light absorbing chromophore to be illuminated during a hair removal 
procedure is naturally occurring, such as melanin in the hair ducts. 
Sample process parameters useful when the pulses of light used in the skin 
pretreatment process of this invention are provided by a Nd:YAG laser and 
the contaminant comprises light mineral oil and carbon particles are as 
follows: 
Wavelength about 1064 nm 
Beam Shape: circle or square 
Beam Size: about 8 mm diameter (circular) or 7.times.7 mm (square) 
Fluence 1-2 J/cm.sup.2 
Pulse energy 0.5 J/pulse 
In some cases it may be advantageous to repeat the pretreatment process 
from 1 to about 3 times before a procedure is attempted to illuminate the 
hairs with sufficient energy to cause hair removal and/or long term 
inhibition of hair growth. Alternatively, for particularly resistant 
sites, the pretreatment of this invention can be alternated with the laser 
hair removal treatment in fairly rapid succession. For instance, success 
has been obtained in the long-term inhibition of growth of a man's beard 
by three repetitions of the pretreatment/treatment cycle, spaced apart by 
a rest period of about 3 to about 5 days. The illumination at pretreatment 
was at 1.5 J/cm.sup.2 to infiltrate the contaminant, and drive the 
follicles into telogen phase. The illumination for hair removal following 
the rest period was at 3.0 Jcm.sup.2. In this embodiment of the invention, 
due to the short rest period, the contaminant introduced during each of 
the pretreatment procedures remained in place and was not replenished 
before the subsequent hair removal treatment, which followed immediately 
after the rest period was completed. 
In yet another embodiment of the invention, the pretreatment method 
comprises the following steps. An oil-based contaminant containing a 
light-absorbing chromophore is applied as described above to the surface 
of a section of skin. The contaminant may be allowed to rest upon the skin 
for a period of time sufficient for the opening of the hair follicle to 
become enlarged, for example, about 15 minutes, before the next step is 
taken. 
Next, a hair removal wax is applied over the oil-based contaminant on the 
skin surface and is allowed to dry. Any commercially available wax 
intended for hair removal can be used, for example Azulene.TM. or 
Ember.TM., both hard waxes, or Epillyss.TM., a soft wax. To adhere the wax 
to the skin surface, application of the wax commences from a location on 
the skin surface just outside the area covered with the oil-based 
contaminant. Adjacent strips of wax should overlap to form a covering that 
completely bridges the oily area and adheres to oil-free skin surface 
around the periphery. Once the wax has been allowed to thoroughly dry 
according to the manufacturer's instructions, the wax is stripped from the 
skin. Surprisingly, in the waxed area a significant proportion of the 
hairs will be removed from the hair follicles even though the wax was 
applied to water or oil-coated hairs. In addition, stripping the wax and 
extracting hairs from the hair follicles causes the light-absorbing 
particles to infiltrate throughout the hair follicles more completely. The 
stripping action also subjects the hair follicles to sufficient shock to 
synchronize hair growth after a rest period is observed, as described 
above. Following the rest period, hair removal procedures can be 
undertaken with the expectation of an increased level of efficiency. 
This aspect of the invention having been fully described, it is further 
illustrated by the examples below. It will be understood, however, that 
the invention is not limited by the examples but is defined by the 
appended claims. 
EXAMPLE 1 
The following set of experiments was conducted to determine the period of 
time required after administration thereto of an irritant or shock for 
hair follicles to enter the late telogen/early anagen stage of the hair 
growth cycle. The data obtained indicates how long the rest period should 
be between administration of the shock and commencement of a hair removal 
procedure. 
The lower left forearm, wrist area, and hand of a human patient was 
selected as the location of the test sites. The untreated right hand and 
arm of the subject was used as a control. The locations on the subject's 
left hand and arm selected as test sites had been lased 2 months before 
this treatment, but 100% of the hairs had grown back. In addition, 
reference photographs of hairs in anagen and telogen phase were used for 
comparison with hairs plucked from the test sites. FIG. 3 shows the 
morphology of a plucked hair in anagen phase, with the full hair matrix 
shown as plucked from the end bulb. The lower portions of anagen hairs are 
soft and malleable, and may have a tendency to bend over after plucking so 
that they appear to be curved, or even hooked at their ends. FIG. 4 shows 
the morphology of a plucked hair in telogen phase. The club-shaped tip at 
the bulb end is the distinguishing characteristic of the telogen phase 
hair. 
The test sites on the left hand, as shown in FIG. 5, were as follows: 
______________________________________ 
site # 
Treatment protocol 
______________________________________ 
1 Pluck hair, lase continuously with multiple passes 5 days after 
plucking 
2 Pluck hair, lase continuously with multiple passes immediately 
after plucking 
3 Pluck hair, no lasing 
4 No plucking; lase continuously with multiple passes 
immediately 
after plucking, close shave hair after lasing 
5 Close shave hair, no lasing 
______________________________________ 
On the right hand, as shown in FIG. 6, the treated sites were as follows: 
______________________________________ 
site # Treatment protocol 
______________________________________ 
6 Close shave hair, no plucking 
7 Close shave hair, no plucking 
______________________________________ 
For lasing, a Nd:YAG laser operating with a wavelength of 1.06 microns, 
repetition rate of 10 Hz, fluence of 3.0 J/cm.sup.2 was used. 
Eventually, all hairs above the skin surface in the test areas were plucked 
(#1-3) or shaved (#4-7). Sites # 5, 6, and 7 are controls for site #4, and 
site #3 is a control for sites #1 and 2. Records of hair regrowth were 
kept for all sites. The time for regrowth to reach a length of 3 mm was 
recorded. The hair was shaved as 3 mm of regrowth was exceeded. Records of 
hair density were also kept. Density was estimated by eye, by comparison 
with shaved and unshaved control areas on the right hand, which showed 
density and appearance at the beginning of the study. One-fourth of the 
hairs from each test site were plucked at each of weeks 1, 2, 4, and 6 
post lasing for examination by microscope to determine the effect of laser 
induced modifications. 
On day 8, hairs from site #7 were plucked for measuring. By comparison with 
the reference photograph of FIG. 3, the hair bulbs showed that the hairs 
were in anagen phase. By contrast, on day 8, hairs from site #4 were 
completely bleached and showed a tapering tip in the place of the hair 
bulb. The results of the tests at day 8 are shown in Table 1 below. 
TABLE 1 
______________________________________ 
# mean 
Site # 
of hairs 
anagen telogen 
tapering 
broken 
length (mm) 
______________________________________ 
4 48 0 3 (6%) 
45 (94%) 
0 2.79 .+-. 0.25 
7 27 24 (89%) 
2 (7%) 1 4.4 .+-. 0.4 
______________________________________ 
FIG. 7 shows a photograph of a hair from site #5 on day 8. The lower 
portion (the bulb) is pigmented (dark brown) and the shape is straight, 
indicating that the hair is in anagen phase. By comparison, another hair 
from site #5 shown in FIG. 8 is transparent, indicating a lack of pigment 
(lack of melanin) and the bulb has a club shape. These characteristics 
indicate the hair is in telogen phase. 
On day 14, hairs from site #4 would slide easily out of the follicle when 
pulled. The tip of the shaft was normally pigmented (pigmentation had 
recovered as compared to the rest of the shaft), but the tip was about 50% 
smaller than the rest of the shaft. Of the 18 hairs plucked from each site 
on day 14, the average length of the whole plucked hair was as follows: 
______________________________________ 
Site #4 2.5 .+-. 0.4 mm 
Site #7 5.4 .+-. 0.6 mm 
______________________________________ 
On day 18, follow-up studies of hairs from sites #4 and #7 were conducted 
by microscopic examination and measurement of plucked hair shafts, with 
the results shown in Table 2 below: 
TABLE 2 
______________________________________ 
# mean 
Site # 
of hairs 
anagen telogen 
tapering 
broken 
length (mm) 
______________________________________ 
4 13 0 1 12 0 7.1 .+-. 0.3 
7 17 15 
1 1 0 2.5 .+-. 0.35 
______________________________________ 
The hairs from sites 4-7 were also measured to determine the length of the 
hairs above the skin and the length of the hairs below the skin. The 
results of these studies are shown in FIGS. 9 and 10. The length of the 
hairs above the surface from lased site #4 clearly showed inhibition of 
hair growth as compared with the length of hairs from control sites. From 
these studies it was determined that 18 days after lasing, the hair bulbs 
for hairs in site #4 were less than 1 mm below the surface of the skin, 
while the hair bulbs of hairs from the control site were at a depth of 
about 2.5 mm beneath the surface of the skin. Thus, the hair ducts of the 
treated site had contracted as a result of being shocked. This data 
confirms that the lasing was sufficient to cause hairs at site #4 to pass 
into telogen phase. 
Discussion of Results 
On the laser treated sites, hair kept growing above the skin surface at the 
same rate as on the untreated (control) site during the first 4-8 days 
after treatment. Growth of hairs on the laser treated sites slowed down, 
then stopped, and the hairs fell out within the next 1-2 weeks. By 
contrast, the hairs on the control site continued to grow, obtaining a 
length that increased linearly with time. 
Anagen and transition stage hairs on the laser treated site showed 
significant morphological changes (tapering at the hair bulb end) as early 
as the 4th day after treatment. This phenomenon continued until the hairs 
fell out. By contrast, telogen hairs remained unaffected by laser 
treatment and continued to follow a normal growth cycle. 
When hairs that showed modifications after laser treatment were plucked, 
they were found to be half as long below the skin surface as were the 
normal untreated hairs (controls). Hairs that were not plucked showed 
bleaching down to the root, and then 1-2 weeks later started to recover 
pigmentation at the tapering end. Slim pigmented "tails" could be seen at 
the recovering end, yet the hairs never returned to normalcy and never 
resumed a normal growth cycle. 
About three weeks after lasing, hairs started growing back in significantly 
reduced number in the laser-treated site. About 20% regrowth was observed 
38 days after laser treatment. No telogen hairs were found on the laser 
treated sites 38 days post lasing, suggesting that telogen hairs were 
unaffected by laser treatment and synchronously cycled into active growing 
anagen hairs. 
Black material in the upper portion of the hair follicles under the stratum 
corneum became visible on the laser treated sites about 2 weeks after 
treatment and remained visible without any signs of hair growth in the 
follicles. The dots of black material did not disappear after extensive 
lasing at 1.06 microns wavelength and 3.0 J/cm.sup.2 fluence. 
EXAMPLE 2 
The procedures of Example 1 were repeated using four human subjects, except 
that four different sites were used for each subject: back, forearm, thigh 
and axilla. Control, unlased sites were also utilized at each of the four 
locations for each subject. FIG. 11 is a graph showing the average length 
of the hair above the skin surface at times zero to 12 weeks after laser 
treatment without waxing, wherein -.circle-solid.- represents the average 
length of the unlased hairs (controls) for the four subjects, and -570 - 
represents the average length of the lased hairs for the four subjects. 
The inhibition of hair growth caused by the mild laser treatment to shock 
the hairs was greatest on the back, thigh and axilla. Growth of hairs on 
the forearm was least affected. 
FIG. 14 is a graph showing the results of measurements over the period from 
days 4 to 12 post lasing to determine the average length of hairs below 
the skin surface for the four subjects wherein -.circle-solid.- represents 
the average length of the unlased hairs (controls) for the four subjects, 
and -.box-solid.- represents the average length of the lased hairs for the 
four subjects. These results show that the shortening of the hair duct (as 
occurs during telogen phase) had begun as early as four days post lasing. 
EXAMPLE 3 
Monte Carlo simulation studies were conducted using known methods to 
calculate the actual fluence profile in human skin or flesh when the skin 
surface is illuminated with a Nd:YAG laser having a wavelength of 1.06 
microns, with fluence in the incident beam of 1 J/cm.sup.2, and energy per 
pulse of 0.5 J. 
Optical and geometrical properties at the wavelength value of 1.06 .mu.m 
are summarized in Table 3 below: 
TABLE 3 
______________________________________ 
Optical Properties for skin model 
.mu..sub.8 
.mu..sub.5 
g n depth (mm) 
______________________________________ 
Epidermis 
2 300 0.85 1.4 0.065 
Dermis 1 100 0.85 1.4 Infinite 
______________________________________ 
The effective penetration depth (L.sub.eff) of light into tissue is 
estimated in general light diffusion theory as follows: 
EQU L.sub.eff =[3.mu..sub.a .mu..sub.s (1-g)]-1/2 
Utilizing the data from the Table 3, the calculated penetration depth 
(L.sub.eff) in dermis is about 1.5 mm. 
In the model, a collimated laser beam is incident on the skin at a right 
angle to its surface. The skin model consists of two domains, which 
imitate the properties of the epidermis and dermis. The epidermis is 
considered as an infinite slab 65 .mu.m wide. The dermis is considered as 
a semi-infinite domain having a common plain interface with the epidermis 
and extending infinitely along the interface. 
Simulation Method 
Propagation of light in skin was simulated by the Monte-Carlo (M-C) method, 
in which absorption and scattering phenomena in highly light scattering 
media has been properly accounted, as well as refraction and reflection of 
light at the interfaces. Software utilizing known mathematical formulae 
was used to make the calculations. 
In simulation, the tissue was divided into a 3D array of small (0.2 mm on a 
side) cubic volume elements, the amount of light energy absorbed inside 
each element was estimated, and the local energy fluence rates were 
retrieved to enable a 3D representation of the radiation level within the 
tissue. In this way, fluence rates in both vertical (radius-depth or r-z) 
and horizontal (x-y) cross-sections were estimated and displayed in 
contour plots. In all simulations, the origin was on the skin surface in 
the center of symmetry of the incident beam. Depth was measured from the 
epidermis-air interface into the tissue. 
For economy of time, the simulation procedure was divided into two stages. 
The first stage included M-C simulation of fluences in a selected cross 
section with a 0.2.times.0.2 mm.sup.2 (pixel) incident beam and a fluence 
rate in the beam of 1 J/cm.sup.2. At the second stage, a desirable beam 
shape was approximated with square beam pixels, and then fluences were 
added up to calculate ultimate fluence rate for each particular beam 
profile and cross section. 
For different skin models or reflector conditions, a new M-C simulation 
with pixel beams was performed. Results of simulations obtained by the two 
stage method has been shown to be identical to those generated with 
conventional M-C, other conditions being equal. 
Cross sectional profiles of fluence rates in the r-z plane of 3.0, 2.5, 
2.0, 1.5, 1.0 and 0.5 J/cm.sup.2 were plotted for fluence in the incident 
beam of 1 J/cm.sup.2 using a 7 mm diameter round beam with energy per 
pulse of 0.5 J. A plot of these fluence profiles is shown in FIG. 13. 
FIG. 14 shows a plot of fluence in skin at depths from zero to 5 mm for 
laser light having the same parameters as in FIG. 13. Fluence is shown on 
the y axis using an exponential log scale. L.sub.eff is shown to be equal 
to about of 1.4 mm. 
The methods of this invention provide several advantages. When the papilla 
is in a position proximate the skin surface, it is more easily reached by 
light energy administered to to the skin surface, and thus is more 
susceptible to damage at low fluence, i.e., in the range from about 3-5 
J/cm.sup.2. Because stem cells are more susceptible to long term damage 
when they are activated, increasing the percentage of the hairs in late 
telogen/early anagen phase increases the number of hairs in any given 
section of skin that are sufficiently damaged by such techniques to effect 
long term inhibition of hair growth. Thus, by utilizing the pretreatment 
method of this invention, the energy required to effect permanent hair 
removal is minimized because the distance below the surface of the skin to 
which light energy must penetrate during a hair removal treatment is 
minimized, and the percentage of hairs for which the future growth is 
significantly inhibited can be increased. Both goals are attained while 
minimizing undesirable damage (burning) of surrounding tissue. 
No. 2: Methods and Devices for Infiltrating Contaminant in Laser-Assisted 
Hair Removal 
Many hair removal procedures involve application of a contaminant 
containing light-absorbing particles to the surface of a section of skin 
for the purpose of inhibiting the growth cycle of hairs in the skin 
section, or for long term inhibition of hair growth in a skin section. The 
skin section and hair ducts therein containing the contaminant are 
illuminated by a beam of light at a wavelength absorbed by the contaminant 
for the purpose of (1) driving particles in the contaminant into the lower 
region of hair ducts (propulsion phase) and (2) causing the particles to 
heat up (thermal phase). Heat is thereby delivered preferentially to hair 
growth cells at the base of the hair ducts. However, it is difficult to 
produce a net downwards vector on a particle sufficient to drive it into 
the depths of the hair duct because light incident upon a skin surface is 
randomly scattered and absorbed during passage through the epidermis and 
dermis of the skin. In addition, sebaceous glands in hair ducts tend to 
exude a sticky wax-like substance that impedes movement of chromophore 
particles into the base of the hair ducts. 
In addition, the skin structures that are targets of various laser 
treatments are found at different depths in skin. It is known to vary the 
wavelength of the laser beam to control the depth to which a laser beam 
penetrates into skin so as to direct laser energy only so deeply into skin 
as is necessary to affect the skin structure that is the target of a 
laser-assisted skin treatment. Further methods of controlling the depth of 
penetration of a laser beam into skin would be advantageous. 
One aspect of the invention solves this problem by providing an improved 
method for infiltrating light-absorbing chromophore particles into hair 
ducts using laser illumination. In one aspect of the invention, a mask is 
interposed between the light source and the skin section to be treated, 
and receives an incident large laser beam, but transmits a plurality of 
small laser beams spaced so as to prevent merging of the beams in the skin 
surface. These small beams are used to create an energy profile with depth 
in skin that is useful for creating a net downward force on illuminated 
chromophore particles in hair ducts to drive the particles into the depths 
of the hair ducts. In another aspect of the invention, an array of lenses 
is substituted for the mask to transform an incident large laser beam into 
a plurality of small beams spaced so as to prevent merger of the small 
beams. 
A beam of light incident upon a skin surface is progressively attenuated 
with increasing depth due to absorption and scattering of photons. The 
gradient in skin of energy attenuation depends upon the beam size. The 
gradient of energy attenuation is relatively flat if the beam of light is 
relatively large (i.e. 7 to 8 mm in diameter). Photons that penetrate skin 
without absorption (i.e., such as those provided by a Nd:YAG laser) tend 
to be randomly scattered during passage. Due to the random scattering 
effect, photons tend to strike a particle of contaminant in a hair duct or 
other skin structures from all directions. In the case of a relatively 
large beam, a particle is bombarded with photons of comparable energy on 
all sides, making it difficult to create a net downward vector on an 
illuminated particle of contaminant, even if some parts of the particle 
are exploded by the light energy. 
It has now been discovered that a small beam of light having a spot size in 
the range from about 0.5 to 1.0 mm in diameter is attenuated more rapidly 
with depth than one of larger diameter (e.g., 8 mm in diameter). Thus, the 
size of the light beam controls the depth at which follicles and other 
skin structures are affected by a light beam. For more shallow effect, the 
beam spot size is decreased. As shown in FIG. 15B, the gradient of energy 
attenuation in skin is correspondingly steeper for small beams, with the 
steepness of the energy gradient progressively increasing as the beam spot 
size decreases. Therefore, either a single small beam producing a spot 
size in the range from about 0.5 to 1.0 mm in diameter or a plurality of 
small beams of light of such size establish in skin a steep light energy 
gradient having rapid attenuation with depth. 
It has also been discovered that small beams of light in this size range 
spread out with depth more rapidly than larger beams (FIG. 15A). 
Therefore, if a plurality of small beams are used simultaneously to create 
a steep energy gradient within skin, the small beams must be spaced apart 
a sufficient distance to prevent the small beams from merging beneath the 
skin surface and taking on the characteristics of a large composite beam. 
Accordingly, the plurality of small beams are usually spaced at a distance 
that approximates the effect of an infinite distance, for example about 
0.5 to 1.0 mm between the circumference of the beam spots. 
Due to the large energy gradient of attenuation established by a single 
small beam (or by a plurality of small beams of light having the 
above-described spot diameter and spacing), a photon from such a small 
beam imparts greater heat energy to the top region of a chromophore 
particle in a hair duct than a photon from the same beam that strikes the 
particle at a lower region. The difference in energy between photons 
striking the top and bottom of a particle infiltrated into skin or into a 
hair duct is larger, the larger the size of the particle. A photon may 
strike the top region of a 1 micron particle with sufficient energy to 
cause a small explosion, but a photon from the same small beam of light, 
or a photon scattered from a nearby beam of light, that strikes the bottom 
of the same particle may have lost sufficient additional energy in 
traveling through skin an extra micron in depth to be incapable of causing 
an explosion at the point of impact. When this effect is multiplied by a 
plurality of photons striking each of the chromophore particles in a hair 
duct, a net downward force is exerted on the particles. This net downward 
force is useful for driving the contaminant particle into the depth of the 
hair duct during laser-assisted hair removal procedures. 
In view of these considerations, in one aspect of the invention a single 
small beam of light is rapidly scanned over the section of skin to be 
treated. For example a single beam having a spot diameter of 0.5 to 1 mm 
in diameter with a fluence of about 2.5 J/cm.sup.2, with pulse energy of 
about 20 mJ per pulse, a pulse repetition of about 600 pulses per second, 
and a minimum pulse duration of about 10 ns could be used to exert 
sufficient force on graphite particles in hair ducts to drive a portion of 
the particles into the base of hair ducts. Once the particles are spread 
into the base of the hair ducts, the laser parameters can be adjusted to 
those recognized in the art as suitable for heating up the particles so as 
to transfer heat to tissue surrounding the hair ducts. When a single small 
beam is used during the propulsion phase, a different laser to provide a 
beam diameter of about 7 to 8 mm is generally used during the heating 
phase of the hair removal process. 
Alternatively, to avoid having to switch lasers between the propulsion 
phase and the heating phase, a device can be interposed between the light 
source and the skin section to be treated that will transform a single 
large beam (e.g., one of 7 to 8 mm in diameter or a 7 mm square beam) into 
a plurality of small beams having the size and spacing disclosed herein. 
One such devise is a light-blocking mask having an opaque body with many 
light-transmissive, small cylindrical apertures, each with a diameter of 
from about 0.5 to 1.0 mm, with a distance of about 0.5 to 1.0 mm between 
the circumferences of the cylinders. For convenience, the mask can be 
adapted for attachment directly to the distal end of a laser wand. 
The body of the masque is opaque and can be in any convenient overall size 
and shape, such as a round or square thin plate, so long as it has one 
surface that is adapted for contacting a skin surface. Generally the body 
of the mask is at least 10 times less in thickness as in overall size to 
prevent the sides of the cylindrical apertures from shading the skin 
surface as the light passes through the apertures. The apertures in the 
body are generally oriented perpendicularly to the contact surface of the 
mask. For convenience in use, the contact surface of the mask generally 
has an area of about 0.5 to several centimeters square and is generally 
smooth enough to pass over the skin surface without abrading it. The 
contact surface of the mask may be planar or may conform to the shape of a 
body part, and may be rigid or somewhat flexible. 
The mask body can be made of any opaque material that will not be destroyed 
by laser irradiation having the energy characteristics with which the mask 
is to be used. Generally, the mask body is heat resistant and will not 
undergo a chemical reaction caused by the laser. The mask body should 
produce a minimum of specular reflection to avoid an undesirable effect on 
the laser, such as might be created if light is reflected back into the 
laser cavity. For example the surface receiving incident light can be 
roughened to reflect light in all directions. In one embodiment, the body 
of the mask is formed of a sheet of fluorescent paper (such as is used for 
aligning optics containing infra red radiation) with pinholes as 
apertures. 
FIG. 16A is a drawing showing a mask 2 with a body 4 having contact area 6 
and pinhole apertures 8. Incident light beam 8 is transformed by the mask 
into a plurality of smaller light beams 9. Attached to the mask is heat 
sink system 5. 
In use, light from a light source, such as a laser, passes through the 
apertures in the mask and is directed to a skin surface and hair follicles 
through the small apertures in the mask, which have a diameter in the 
range from about 0.5 mm to 1 mm and are spaced apart at a distance of 
about 0.5 mm to 1 mm as measured between the edges of the apertures. The 
size of the apertures and their spacing or density in the body of the mask 
are selected to create from the large light beam a plurality of small 
beams. For example, a mask for use with a Nd:YAG laser having a wavelength 
of about 1064 nm and a beam size of about 8 mm contains round apertures 
with an internal diameter of about 0.4 to about 0.8 mm and an average 
spacing between edges of the apertures of about 0.5 to 1.0 mm. 
Since the mask screens out a substantial portion of the light energy 
produced by the light source, several passes of the masked light source 
over a section of skin are required to deliver the same amount of light as 
does an unmasked light source. A simple calculation can be used to 
determine the number of passes of light delivered through a mask having 
apertures of any given diameter and density are required to approximate 
the energy delivery of a single pulse of unmasked light. The following 
sample calculation shows the light delivery of a mask having apertures 
with a diameter of 0.6 mm and a density of 60 apertures/cm.sup.2 : 
Diameter of a hair follicle=0.1 mm; 
Diameter of mask aperture=approximately 0.6 mm 
Effective area S covered by a single aperture=3.14 (aperture dia.+follicle 
dia).sup.2 
Area covered by a mask with 60 apertures/cm.sup.2 after 5 
passes=5.times.60.times.S=1.15 cm.sup.2 
By this calculation, 5 passes of a laser beam of 8 mm in diameter delivered 
through a mask having an aperture density of 60 apertures/cm.sup.2 
delivers to a single hair duct approximately the same energy as one 
unmasked pulse. 
Therefore, several pulses delivered through the mask are required to 
delivery laser energy equivalent to 1 to 2 pulses of unmasked light. 
Generally, about 5 or 6 pulses are delivered to each section of skin 
treated, with the mask being shifted slightly at random between the pulses 
to even out the amount of illumination. In general, whatever the diameter 
and density of the apertures in the mask, the number of lasing passes with 
the mask in place is selected to deliver roughly the same amount of energy 
per hair duct or other target skin structure as would be received from 
unmasked light. 
In one embodiment, the body of the mask is adapted to absorb heat from the 
surface of the skin during its illumination. The body of the mask can 
absorb some quantity of heat from the skin surface, depending upon the 
heat capacity of the material from which it is made. The capacity of the 
mask body to absorb heat can be enhanced by having one or more passageways 
or conduits there through in which a cooling medium is circulated to 
absorb heat from the skin surface. For example, at least one conduit for 
the cooling medium can be located around the periphery of the body of the 
mask in a portion of the body that does not contain the apertures. In 
addition, as shown in FIG. 15, any known type of heat sink system 5 can be 
attached to body 4 of the mask, including those provided by thermoelectric 
cooling, passive heat sinks, convection cooling, such as provided by fans, 
conduction cooling, prechilling, and the like. 
When used as described herein, the mask provides the advantage of 
increasing the net downward force vector on light-absorbing particles in 
the hair ducts caused by light photons delivered through apertures in the 
mask. The mask also decreases the depth of penetration through skin of an 
incident light beam and therefore, is useful in any skin treatment in 
which a shallow penetration of light is required. 
In another aspect of the invention, an array of lenses (FIG. 16B) is 
substituted for the mask to transform an incident large laser beam into a 
plurality of small beams having the above described spot size and spaced 
at an interval to prevent merger of the small beams. The array includes a 
plurality of lenses, each having a focal length of about 5 mm to about 50 
mm and a diameter of about 5 mm to about 50 mm. Although the array can 
have any overall shape, in one embodiment the lenses in the array are 
disposed to receive an 8 mm diameter incident beam and transform it into a 
plurality of beams having a spot size of about 0.5 mm to about 1.0 mm. As 
shown in FIG. 16B the array 84 is arranged circularly, with each lens 86 
being semispherical in shape. The array can be either flat or curved. In 
use, the lenses can be disposed in either direction relative to a skin 
surface. 
The mask or the array is adapted for attachment to a laser wand or laser 
arm for delivering the small beams to the skin surface during treatment by 
laser irradiation. Although these devices are described with reference to 
the advantages of creating a steep energy gradient within skin to 
facilitate creation of a net downward vector on particles infiltrated at 
some depth within skin structures, such devices can also be used to create 
a plurality of small beams to facilitate shallow illumination of a skin 
surface for any purpose, such as might be useful in a method of laser skin 
peeling or to affect sebaceous glands. 
No. 3: A Method for Infiltrating a Contaminant into Hair Follicles Using an 
Occlusive Dressing 
Hair removal procedures are known in which a contaminant is applied to the 
skin surface and caused to infiltrate into hair ducts for subsequent 
irradiation by a light source. To effect hair removal, the light absorbing 
contaminant (usually containing light-absorbing particles) must be driven 
to a depth in the hair duct that will allow transfer of heat and 
mechanical energy from the particles directly to tissue surrounding the 
hair duct that effects hair growth, Le., the stem cells located in the 
bulge area and the dermal papilla of the hair duct. Generally, however, 
massage of the contaminant onto the skin surface causes the contaminant to 
infiltrate the hair ducts only for about 20 microns, yet the portion of 
the hair duct that contains the stem cells and/or dermal papillae is 
located at a depth of from about 2 to 6 mm, depending upon the location on 
the body where inhibition of hair growth is desired, i.e., the beard, leg, 
or upper lip. 
The present method provides a procedure by which a contaminant, once 
applied to a skin surface so as to introduce the contaminant into the top 
region of the hair follicle, can be induced to infiltrate more deeply into 
the hair follicles to be treated. In the present invention, after 
application of the contaminant to the skin surface, but prior to 
illumination, the pores and infiltrated hair ducts in the skin section are 
occluded for a period of time ranging from several minutes to several 
hours, whereby further infiltration of the contaminant into the hair ducts 
is caused. 
The invention is described with reference to FIG. 17, which shows occlusive 
dressing 10 covering a section of skin 12 to which a contaminant 14 
containing particles has been applied and infiltrated into hair ducts 31. 
It has been discovered that when an occlusive covering is applied to a 
contaminated skin section for an extended period of time, contaminant in 
the upper region of the hair ducts is drawn into the lower portion of the 
hair ducts as shown in FIG. 18. Therefore, occluding the contaminated hair 
ducts with a covering facilitates loading of particles in the contaminant 
into the lower regions of the hair ducts. This discovery provides an 
alternative method for spreading a contaminant, such as one containing 
light absorbing particles, deep into the hair follicles prior to 
illumination so that, during illumination of the skin section, the heated 
particles will transfer energy to the portion of the hair cells 
surrounding the lower region of the hair follicle that are responsible for 
hair growth, particularly those in the bulge area. 
Any air and water-tight covering can be used as an occlusive dressing. For 
instance, any type of known liquid that can be painted or sprayed onto the 
skin to form an occlusive covering can be used. In addition, an occlusive 
bandage or dressing that provides an adhesive seal at the skin surface 
around the perimeter of the covered area can also be used. For example, 
the occlusive dressing sold under the trade name Tegaderm.TM. bandage can 
be used to occlude the contaminated skin section. 
Allowing the occlusive covering to remain on the contaminated skin surface 
for an extended period of time is sufficient to induce infiltration of the 
contaminant into the lower regions of the hair follicles. The period of 
time required will vary, depending upon the depth of the hair follicles to 
be treated. Once this goal has been accomplished, the occlusive covering 
can be removed from the skin surface, and the skin surface is ready to be 
illuminated to cause injury to or destruction of the cells surrounding the 
hair ducts that promote hair growth. 
Generally, the covering is allowed to stay in place for a period of time 
ranging from several minutes to several hours, for example about 15 
minutes, whereby infiltration of the contaminant into the lower regions of 
the hair follicles is induced. Infiltration is optionally further enhanced 
by application of a surface-wetting agent to the skin surface. A surface 
wetting agent will facilitate wicking of the contaminant, including any 
chromophore particles contained therein, into the hair ducts while the 
pores and hair ducts in the skin surface are occluded, i.e., while sealed 
with a water-barrier forming substance, or covered with an impermeable 
patch or bandage. The surface wetting agent can be added to the 
contaminant, or contained within or upon the occlusive dressing. All that 
is required is that the surface-wetting agent is present at the mouth of 
the occluded follicles during the period of time that the occlusive 
covering is in place. 
After removal of the occlusive covering, the skin surface can be 
illuminated to shock or cause injury or destruction of the cells 
surrounding the hair ducts that promote the growth of hairs. Any of the 
methods of illumination that utilize a light absorbing contaminant in 
conjunction with a light source, such as a laser with a wavelength of 
light highly absorbed by the contaminant can be employed during the 
illumination phase. Examples of such methods and procedures, and of the 
most useful types of contaminants and lasers, are described in full in 
U.S. Pat. Nos. 5,226,907 and 5,425,728, which are incorporated herein by 
reference, each in its entirety. 
For example, laser illumination to inhibit hair growth can be accomplished 
by infiltrating a contaminant containing carbon particles in the size 
range from about 0.01 micron to about 1 micron into hair ducts on a 
section of skin and then illuminating the skin surface with light from a 
Nd:YAG laser. Generally the temperature of the contaminant is raised to 
70.degree. C. to 80.degree. C. for about 0.1 second by this method. Energy 
transferred from the heated contaminant in the hair ducts to skin tissue 
surrounding the hair ducts provides long term inhibition of hair growth in 
the hair ducts. Since the wavelength produced by a Nd:YAG laser penetrates 
skin with a minimum of absorption and scattering therein, overheating of 
surface skin tissue is avoided. 
In another embodiment of the invention, the occlusive covering comprises a 
flat, flexible supporting scrim covered on one or both sides with a 
hydrogel. The scrim is generally a plastic lattice or cloth netting upon 
which the hydrogel is placed. The hydrogel is a three-dimensional 
polymeric network that can solvate a large quantity of water without 
dissolving. The copolymer can contain both hydrophilic and hydrophobic 
components. The hydrophilic monomers used are generally 
N-vinyl-2-pyrrolidone (VP), 2-hydroxyethyl methacrylate (HEMA), and 2 
acryloylamido-2-methylpropanesulfonic acid (AMPS). Copolymerization with 
other hydrophobic monomers is generally carried out in the presence of 
crosslinking agents, such as divinyl benzene (DVB) and ethylene glycol 
dimethacrylate (EDMA). Examples of commercially available 
hydrogel-containing products suitable for use as an occlusive covering are 
as follows: 
______________________________________ 
Product 
Hydrogel Polymer 
Supporting Scrim 
______________________________________ 
Second Skin .RTM. 
Poly (ethylene Oxide) 
polyethylene (PE) nonwoven 
scrim (Mfg. 
Spenco) inter- 
layer with 
peelable poly- 
ethylene backing 
CuraGel HEMA:PEG:N.dbd.C--O 
nonwoven cotton gauze on- 
elastomer (Mfg. Kendall) 
substrate with PE backing 
TTL Medical 
HEMA:PEG:N.dbd.C--O 
isolated nonwoven fibers. On 
elastomer (semi-occlusive ure- 
thane dressing) substrate with 
PE backing 
______________________________________ 
Hydrogels are composed mostly of water, for example greater than 80% by 
weight, immobilized in a matrix of a hydrophilic crosslinked polymer. One 
of the unique characteristics of hydrogels is that, due to crosslinking of 
the polymer system, they do not dissolve in the water they hold. The 
result is "trapped water" held by solvation to the hydrophilic portions of 
the hydrogel. To take advantage of these characteristics, when a hydrogel 
is used as the occlusive covering in the practice of this invention, it is 
usually not removed prior to lasing. Therefore, preferred hydrogels are 
those which provide optimal optical transmissivity and form a minimum of 
toxic products during lasing. Urethane gels may contain unreacted 
isocyanates, which have a distinct odor, and present a possibility that 
potentially hazardous pyrolites can be formed upon lasing, such as is 
formed by cleavage of common aromatic isocyanates. Consequently, the 
"urethane" type of HEMA:Poly(Ethylene Glycol):isocyanate hydrogel is 
useful, but poly (ethylene oxide) hydrogels are preferred if the hydrogel 
is to remain in place during lasing. Such PE hydrogels contain no hydrogen 
atoms and cannot form toxic by-products. 
One of the advantages of leaving the hydrogel in place during lasing is to 
contain the contaminant and drive the contaminant downwards within the 
hair ducts. FIGS. 18A-18F illustrate how these advantages are achieved. If 
the occlusive dressing is removed, force vectors generated during lasing 
may spill the contaminant out of the hair follicle (shown in FIG. 18C). 
During lasing a short pulse of energy vaporizes some of the contaminant, 
and a puff of smoke and fragments is produced, which fly off the skin 
surface as smoke or particles. In the present invention, the hydrogel 
serves as a blast barrier, to confine the smoke and fragments so formed. A 
particle or fragment in a hair duct is forced downward into the hair ducts 
(FIG. 18D). In addition, a portion of the water in the hydrogel 
evaporates, providing an additional instantaneous overpressure, shock, and 
acceleration to aid in propelling the chromophore into the depth of the 
follicle. Steam so created may instantaneously lift the hydrogel from the 
skin surface, but unvaporized water remaining in the hydrogel rapidly 
cools the laser-induced steam back to water, causing the hydrogel to 
"slap" against the skin surface. This "slap" may help propel the 
contaminant into hair follicles. Because the water content of the hydrogel 
is not compressible, it acts like a solid to the extent that it confines 
the force vectors of an exploding contaminant particle much in the same 
way that a sheet of plastic or glass placed over the skin surface prior to 
lasing would do (shown in FIG. 18E). Therefore, the hydrogel directs the 
energy of the ablation or explosion downward, helping to force the 
contaminant into the depths of the hair ducts (FIG. 18F). 
The water in the hydrogel, which has a high specific heat, can absorb heat 
generated during lasing. As the hydrogel lies atop the skin to be treated, 
its heat absorbing properties afford a unique means for preventing 
overheating of dermal tissue during laser hair removal techniques of all 
types. Further, it has been discovered that the hydrogel can be precooled 
or even frozen prior to application to the skin surface to provide an 
extra measure of cooling to the dermal tissue prior to the lasing phases 
of any hair removal procedures. A hydrogel dressing can be used to cool 
the skin surface whether the cooled or frozen occlusive dressing is 
removed during lasing or not. Studies have shown that light is 
satisfactorily transmitted through a hydrogel dressing when the hydrogel 
remains in place during lasing. 
No. 4: A Soothing Topical Hydrogel Dressing 
Many patients experience some discomfort for a day or two following laser 
skin treatments, such as treatments for skin rejuvenation or to inhibit 
growth of hair. There are many types of prior art bandages and skin 
patches that can be applied to skin surfaces and which release active 
agents useful for reducing minor irritation, inflammation and pain. One 
such device disclosed in U.S. Pat. No. 5,474,528 is a hydrogel skin patch 
that releases a photoactivated pharmaceutical agent to skin when 
illuminated with light, for example during laser therapy. However, it 
would be useful to have a hydrogel composition for application to skin 
that releases active agents for soothing and comforting irritated and 
inflamed skin without recourse to light energy. Such a composition would 
be particularly useful after laser therapy to reduce and/or alleviate 
irritations and inflammations. 
The present invention is a soothing dressing for irritated skin comprising 
a cross-linked polymeric hydrogel matrix into which has been infused a 
hydrating agent, such as water, and an active agent useful for eliminating 
or alleviating a skin irritation, sensitivity or reddening. The hydrogel 
matrix can be made of any species of the wide classes of hydrogels, 
including but not limited to, polymers of acrylates, ethylene oxides of 
various molecular weights, vinylpyrrolidones, natural chitins, lectins, 
and various copolymers thereof. In one embodiment of the invention, the 
hydrogel matrix includes a sufficient amount of an adhesive hydrogel that 
the hydrogel dressing will self-adhere when applied to skin. U.S. Pat. No. 
5,143,071 to Keusch et al. cites an extensive list and description of 
prior art adhesive hydrogels that adhere to skin surface with an intimate 
physical contact. Generally, the polymeric hydrogel will contain up to 84 
percent by weight of water when fully hydrated. For example, the hydrogel 
can contain from about 60 percent to about 84 percent by weight of water, 
or from about 40 percent to about 60 percent by weight of water or other 
hydrating substance, such as an active agent in an aqueous solution. 
The hydrogel dressing may further comprise a scrim with a hydrogel lining 
one or both sides of the scrim. The scrim is generally a plastic lattice 
or cloth netting for supporting the hydrogel, as described in Section No. 
3 above. It is also contemplated that the hydrogel dressing can comprise 
two or more hydrogel layers bonded together along their faces, such as is 
described in Section No. 3. Such a scrimless composite hydrogel is more 
flexible than those with internal scrims and better suited to conform to 
body contours. 
The hydrogel further comprises one or more of any type of active agent that 
would be beneficial for soothing and/or protecting reddened, irritated or 
inflamed skin. For example, the active agent can be an over-the-counter 
drug or folk remedy that serves as a mild antiseptic, an anti-inflammatory 
agent, or a topical anesthetic. Examples of useful active agents include 
benzocaine, hydrocortisone or hydrocortisone diacetate, aloe vera extract 
(available in freeze-dried form), and vitamin E. Rose oil is an example of 
a naturally soothing oil with a pleasant fragrance that can be added to 
the hydrogel as a perfume. Water soluble active agents are dissolved into 
water and the solution is used to hydrate the hydrogel. Oily active agents 
can be emulsified and the emulsion can be dispersed into an aqueous 
component for use in hydrating the hydrogel. 
The soothing action of the active agents is greatly enhanced by effective 
delivery of the agents from the aqueous medium. Introduction of the active 
agent from the hydrogel into hydrated skin tissue, or through the hydrated 
stratum corneum, can be by diffusion, by absorption, or by any other 
mechanism constituting chemical permeation or penetration of the hydrated 
skin or stratum corneum. It is well established in the literature of 
chemical transport through skin that hydration can enhance the chemical 
transparency, transmissiveness, passage, or transport of pharmaceuticals 
through the stratum corneum. A review of the subject of enhanced transport 
of chemical agents across the stratum corneum in hydrated skin is found in 
Ghosh et al., Pharmaceutical Tech., April 1993, which is incorporated 
herein by reference. 
When hydrated, the hydrogel dressing forms a thin relatively transparent 
layer on the skin surface. If the hydrogel layer that is placed against 
the skin is one of the mildly adhesive tacky hydrogels disclosed above, 
the hydrogel dressing is self-adhering and is relatively unobtrusive on 
the skin. This type of self adhesive hydrogel dressing is much less 
noticeable from a few feet away than a reddened mask of irritated skin. A 
tacky hydrogel will adhere to skin so that the dressing will continue to 
release the active agents over a period of many hours, for example about 8 
to about 24 hours. Alternatively, any suitable adhesive known in the art 
can be used to affix the hydrogel dressing to a skin section to be treated 
so that it will remain in place until it is removed by the patient, or 
falls apart in the shower or by wear and tear. However, care should be 
taken that as much as possible of the outer surface of the hydrogel 
dressing is not covered by the adhesive, but is exposed to the ambient air 
during the time the dressing is worn by the patient. With this precaution, 
the hydrogel dressing will administer the soothing active agent(s) to the 
skin to be treated over an extended period of time in slow release as the 
water in the hydrated hydrogel slowly evaporates due to contact with 
ambient air and the body heat of the patient. Natural evaporation of water 
from the hydrogel dressing, which can be re-wet from time to time, 
provides an additional cooling and soothing effect to irritated skin. 
The hydrogel dressing of this invention provides an improved slow release 
vehicle for administration of soothing active agents to a skin surface 
without application of light to the dressing. The dressing is less 
obtrusive visually than standard gauze and tape dressings, and is 
specifically designed to be used following cosmetic laser skin treatments, 
such as treatments for hair removal or skin rejuvenation. 
No. 5: Exposure-Indicating Hydrogel Composite for Laser Applications 
During application of a laser to a skin or tissue surface, certain cell 
particles and pathogens contained in the treated tissue, such as viral 
particles, may become air-borne. In addition, some degree of smoke and/or 
odor may be produced. It is known to cover the tissue to be lased with a 
transparent film or hydrogel to reduce the level of air-borne skin 
products that may put the laser operator at risk. However, such coverings 
obscure the treatment site so that it is difficult to see and keep track 
of which areas have been treated and which have not. 
The present invention provides a scrim-less hydrogel with an 
exposure-indicating layer for covering a surface area to be treated by 
laser. Hydrogels, being mostly water, are fragile and have little tear 
strength. In certain hydrogels, a supporting scrim, which is usually a 
plastic lattice or cloth netting, provides a structure upon which the 
hydrogel is placed, along one or both sides. The supporting structure 
within these prior art hydrogel compositions absorbs some energy from the 
laser. More importantly, the interior scrim limits the elastic modulus of 
the hydrogel and, hence, its ability to conform well to the contours of a 
body upon which it is placed for use as a covering. 
In the present invention, the supporting interior scrim is eliminated to 
reduce laser energy absorbed by the composite hydrogel, for example, when 
laser energy is administered to a skin or tissue surface covered by the 
composition to reduce air-borne particles and/or to aid in propulsion of a 
contaminant into hair ducts. Rather than having an interior scrim, the 
composite hydrogel of the present invention contains at least two hydrogel 
layers firmly attached or bonded together along their faces. The 
attachment can be of any type that forms a substantially transparent bond 
between the two hydrogel layers, for example by lamination. It is 
preferred that the bond between the hydrogel layers have an absorbence 
coefficient of no more than about 1% to about 5%, or an optical 
transmission of from about 95% to about 99%. 
The composite hydrogel is described with reference to FIG. 19A as follows. 
The hydrogel composite 22 comprises at least two hydrogel layers. One of 
the two layers is a film 24 of a thermoplastic or solution-cast hydrogel 
polymer with fewer hydrophile sites in its architecture than is used for 
the material which comprises the bulk of the laminate, the hydrogel layer. 
The hydrogel film is selected to allow a maximum water uptake or swelling 
of about 15% to about 25% by weight. The composition of the thermoplastic 
hydrogel film is selected to provide tear strength to the composite 
hydrogel sufficient to withstand application of the composite to a 
contoured body surface while maximizing the elastic modulus of the 
composition. The second of the two layers is a layer 26 of crosslinked 
polymeric hydrogel. Such crosslinked polymeric hydrogels will typically 
hydrate and swell to a water content of about 75 percent to about 95 
percent by weight of water. One face of the thermoplastic hydrogel film 
and of the polymeric hydrogel layer are permanently attached or bonded 
together so as to minimize the light absorbence at the bond 28. 
The thermoplastic hydrogel layer is referred to as a "film" while the 
cross-linked polymeric hydrogel is referred to as a "layer" to indicate 
the relative thickness of the two layers. Generally the film is no greater 
in thickness than is required to hold the composite hydrogel together 
during use. Excess thickness in the thermoplastic hydrogel will impair the 
flexibility of the composite and its ability to conform readily to 
contoured body surfaces. Generally, the total thickness of the composite 
hydrogel is in the range from about 2 mm to to about 5 mm. 
To indicate the track of the laser beam over the surface of the hydrogel 
composite during use, in one embodiment shown in FIG. 19 the exterior 
surface of the thermoplastic hydrogel film (i.e., the one not attached to 
the layer of crosslinked polymeric hydrogel) has a coating 30 of an 
indicator material. The coating can be partial, for example in a 
discontinuous or openwork pattern. Alternatively, the coating can be 
eliminated if the hydrogel film incorporates an indicator material such as 
a photoactivated dye or chemical. The indicator material is selected to 
change color upon illumination with at least one frequency of light, such 
as is provided by a laser. For use with any known laser, the indicator 
material is selected to change appearance, for example, change color, when 
subjected to the light of the laser to be used. 
The indicator material and its pattern of coating should be selected to 
perform its indicator function while absorbing a minimal amount of light 
energy. For example, the coating of indicator material can be a partially 
metallized surface, such as is formed by vacuum evaporation of aluminum or 
other metal space. It has been found that vapor-deposited metal films, for 
example of aluminum or vacuum-coated bismuth, change appearance when 
illuminated by infrared such as is provided by a Nd:YAG laser at a 
wavelength of about 1 micron. 
The indicator material can also be a photoresponsive pigment, such as iron 
oxide, rhodamine red, or phthalocyanine blue, printed over the exterior 
surface of the thermoplastic hydrogel layer in an open-work pattern, such 
as a pattern of dots 32, intersecting lines 37, or cross-hatched lines 39, 
as shown in FIG. 19B. Certain pigments, such as Monastral Blue.TM. 
(phthalocyanine) and bismuth trioxide will react to infrared light. 
Monastral Blue.TM. pigment also changes appearance when illuminated by 
light in the visible region, for example under the red light of a ruby 
laser. Bismuth trioxide or bismuth subcarbonate, rather than being 
"bleached" by the laser energy, are reduced to the metal by the light, 
resulting in a darkening of the lased area. This phenomenon can be 
beneficial for blocking exposure of the lased area of skin upon subsequent 
passes of the laser, if desired. 
To minimize the laser absorption of the open-work pattern, it can be 
printed in a half-tone, for example a fine half-tone. Generally the ratio 
of the surface area covered by the indicator material to that not covered 
by the indicator material (e.g. the open spaces between the dots) is in 
the range from about 1:5 to about 1:10. It is preferred that the area not 
covered by the indicator material be about 90%, or more, to allow 
visualization of the laser-affected areas while minimizing attenuation of 
the therapeutic radiation. The object is to deposit only enough indicator 
material on the surface of the hydrogel film to be visible to an operator, 
but not enough to substantially reduce the therapeutic radiation reaching 
the patient. 
Examples of crosslinked polymeric hydrogels and thermoplastic hydrogels 
suitable for use in making the thin film 24 of the composite hydrogel 
include elastomeric polymers, such as polyurethane, having hydrophilic 
sites in the polymer molecule of polyethylene glycol and a molecular 
weight of less than about 1,000 units, for example from about 400 to about 
600 units. The supporting film does not imbibe as much water as hydrogel 
layer 26, but retains its ability to transport water to the air, allowing 
some evaporative cooling and oxygen transfer to take place. Examples of 
hydrogels suitable for making layer 26 of the composite hydrogel include 
any of the commercial classes of hydrogels, such as the urethane type 
having hydrophilic sites comprising polyethylene oxide and a molecular 
weight of from about 1,000 to about 2,000 units. Alternatively, any of the 
common commercial classes of hydrogels can be used for layer 26, such as a 
hydroxyethyl methacrylate or a electron-beam crosslinked high-water 
content polyethylene oxide hydrogel, such as is sold by Thermedics, Inc., 
Woburn, Mass. Generally the hydrogel used for making layer 26 is capable 
of imbibing greater than about 80% by weight of water. Because of 
supporting film 24, certain tear-resistant polyethylene oxide types of 
hydrogel that have not been cross-linked by an electron beam have been 
used in prototypes of these laminates. Due to the high water content of 
layer 26, the composite hydrogel is flexible and readily conforms to body 
contours. 
The water imbibed by the hydrogel composite can optionally contain an 
active agent for alleviating pain, reducing irradiation, etc. During use, 
laser irradiation will aid in releasing the soothing active agent to the 
skin surface. Examples of active agents useful for soothing skin are 
described in Section No. 3 of this application. 
Methods of making hydrogel compositions are known in the art and are not 
repeated herein. One skilled in the art can readily modify existing 
methods to fabricate the exposure-indicating hydrogel composite of this 
invention. For example, in one embodiment, the composite hydrogel is 
obtained by a method comprising the following steps. A film is extruded of 
one or a combination of thermoplastic hydrogel polymers that typically 
hydrate and swell to contain a water content of about 15% to about 25% by 
weight of water. The extruded film is laminated to a preformed layer of a 
crosslinked polymeric hydrogel that will hydrate and swell to contain a 
water content of about 75% to about 95% by weight of water. The remaining 
free surface of the thermoplastic hydrogel film is coated in an open work 
pattern with an indicator material that changes appearance upon laser 
irradiation, but absorbs a minimal amount of light energy. If the 
indicator material is a metallic substance, such as aluminum, the coating 
can be applied using a technique of vacuum evaporation. If the indicator 
material is a photoresponsive pigment, such as iron oxide, rhodamine red, 
or phthalocyanine blue, the coating can be printed in an open-work 
pattern, such as a pattern of dots or intersecting lines. One skilled in 
the art will be able to select an indicator material that is activated by 
the light of the particular laser wavelength desired for use in a skin 
treatment process. All that is required is that the indicator material 
change appearance when illuminated by a laser with the particular 
wavelength of light selected for use without being completely 
photo-ablated from the surface of the composite hydrogel. 
In use, the exposure-indicating hydrogel composites of this invention are 
hydrated and placed over a skin surface for laser treatment, with the free 
surface of the crosslinked polymeric hydrogel layer against the surface of 
the skin. The surface of the composite with the coating of indicator 
material does not contact the skin surface, but faces away, so that the 
indicator material can be readily seen by a laser operator. A light beam 
to be applied to a skin surface is transmitted through the hydrogel 
composite to a skin surface with which it is in contact. As the light of 
the light beam strikes the indicator material, the track of the beam 
causes a photoactivated change of appearance in the indicator material. As 
a result, an operator can readily determine exactly which areas of the 
skin or other tissue covered by the hydrogel composite have been treated 
by the light beam. The hydrogel composites are particularly well suited 
for use as an occlusive dressing in the methods described in Section No. 3 
above, in which the occlusive dressing aids in propulsion of chromophore 
particles into hair ducts and other skin structures. 
When hydrated and placed over a skin surface prior to treatment with a 
light beam, the exposure-indicating hydrogel composites described herein 
cool the skin surface by evaporation of water from the hydrogel, and 
prevent generation of air-borne particles of tissue. In addition, they 
absorb less light energy and conform more readily to body contours than do 
hydrogels that contain an interior scrim. Due to a photoactivated 
appearance change caused by the laser in the indicator coating, such as a 
color change, these compositions offer the additional advantage of 
recording the track of the laser over the skin surface to aid the laser 
operator in keeping track of which areas have been treated, and which have 
not. In methods of hair removal or skin rejuvenation, these composite 
hydrogels can also be used to aid in the propulsion of chromophore 
particles into hair ducts for use in inhibiting hair growth, or beneath 
surface skin cells to be removed in skin peeling operations. 
No. 6: A Method for Controlling Thermal and Mechanical Damage During Laser 
Hair Removal by Selecting Chromophore Particle Size 
Hair removal techniques are known that rely upon the transfer of heat 
energy to hair follicles to inhibit hair growth. By raising the 
temperature of tissue surrounding the hair ducts and maintaining it at the 
elevated temperature for a sufficient period of time, the target tissue is 
destroyed, e.g., by thermal coagulation of the hair follicle and of tiny 
blood vessels that nourish the follicle. 
In laser treatments to inhibit hair growth, it is known to infiltrate a 
contaminant containing light-absorbing chromophore particles into hair 
ducts, and then illuminate the skin surface containing the 
contaminant-filled hair ducts with short pulses of light at a wavelength 
absorbed by the contaminant. Chromophore particles absorb short pulses of 
high energy light and either explode, releasing the energy in the thermal 
and mechanical forms, or do not explode and transfer the absorbed energy 
in the form of heat to surrounding tissues by thermal conduction. It would 
be advantageous to control the delivery of mechanical and/or thermal 
damage to the tissue surrounding hair ducts with the goal of inhibiting 
future growth of unwanted hair while avoiding significant damage to the 
surface of the skin. 
Whether pulses of light having a given pulse duration and fluence will 
cause a chromophore particle to explode or heat up depends upon the size 
of the particle. In one embodiment of the invention, the chromophore 
particle size is selected to preferentially induce either thermal or 
mechanical damage to the tissue surrounding hair ducts into which a 
contaminant containing chromophore particles is infiltrated for use in a 
hair removal procedure. In other embodiments, the particles in the 
contaminant have two different sizes or a bimodal size distribution with 
the portion of larger particles determining the proportion of mechanical 
damage desired and the portion of smaller particles determining the 
proportion of thermal damage desired. 
The practical upper limit on the size of chromophore particles used for 
infiltration into hair ducts to effect hair removal is the diameter of a 
hair duct, which is from about 70 .mu.m to about 1 micron for human hairs. 
If a hair duct contains a hair, even smaller particles are generally used. 
Another practical consideration that affects the size of particles used in 
hair removal techniques is the prohibitively high cost of manufacturing 
uniformly sized particles in the submicron size range, such as uniformly 
sized carbon particles. Generally, for this reason, particles in this size 
range are obtained by grinding larger particles. The result is particles 
having a range of sizes, rather than uniformly sized particles. Even if 
the particles are uniform in diameter, due to their small size, they tend 
to clump together in aggregates. For example, the fullerene molecule 
(C.sub.60) has the shape of a soccer ball with a calculated diameter of 
about 0.7 nm, but aggregates of C.sub.60 reach 200 .mu.m in size. 
Therefore, chromophore particles used in hair removal generally have a 
wide size distribution, generally in the range from about 0.01 .mu.m to 
about 1 .mu.m. 
Carbon in the forms of graphite, carbon black, and fullerene is an 
excellent photon absorber and is available in particles having a wide 
range of sizes. Fullerene is available in particles or aggregates ranging 
in size from about 0.7 nm to 200 .mu.m in size. Particles of carbon black 
range from about 10 nm to 500 nm in diameter, depending on the method of 
production. Graphite can be ground to form particles having a wide size 
distribution with an average size down to one micron. Particles can also 
be powder, or even pure carbon dust in one extreme. Any of these 
micro-particles of carbon can be loaded into hair follicles, whose 
diameter for human hairs is in the range from about 100 .mu.m to 10 
microns. 
A contaminant with a bimodal size distribution is readily obtained by 
mixing together two groups of particles with different modal 
distributions, one relatively larger, and one relatively smaller. 
In general, light absorbing chromophore particles of a relatively larger 
size will vaporize or explode when illuminated with at least one short 
pulse of light at sufficiently high power and a sufficiently short pulse 
duration. A consequence of vaporization is the shattering of the particle, 
with propulsion of the fragments into the depths of the hair follicle and 
into the surrounding cells. While vaporization of the contaminant 
particles is highly desirable for forcing the contaminant particles into 
the bottom of hair ducts, the most significant damage particles of this 
size can impart to tissue is cellular damage resulting from direct 
photomechanical disruption of the cellular membrane and other cellular 
structures. When the exploding particles are confined within a hair duct, 
the membranes of cells adjacent to the exploding chromophore are disrupted 
by the shock wave and by the exploded fragments of the particle bombarding 
the surrounding cells. The photomechanical effect of utilizing the larger 
size particles can be enhanced by using pulses in the nanosecond range of 
duration, for example about 1 to about 20 nanoseconds. 
Other factors that influence whether a chromophore particle will explode or 
merely heat up when irradiated with short pulses of light of given pulse 
duration, frequency and fluence, are the physical properties of the 
particular chromophore used, such as its latent heat of vaporization and 
photon absorption coefficient. The photon absorption coefficient of 
graphite when irradiated with light having a wavelength of 1064 nm is 
estimated to be from about 1.times.10.sup.5 cm.sup.-1 to 2.times.10.sup.4 
cm.sup.-1 (T. Barrett, Absorption of Light by Small Spherical Particles in 
a Liquid, ThermoTrex Corporation and T. Barrett, Handbook of Carbon, 
Graphite, Diamond and Fullerenes, Noyes Publications, Park Ridge, N.J., 
1993). The corresponding depths to which the light will penetrate in a 
carbon particle before its energy has been absorbed, (i.e., the light 
penetration depth in carbon corresponding to the above range of photon 
absorption coefficients) is from about 0.1 .mu.m to about 0.5 .mu.m, 
respectively. 
The present invention is illustrated with reference to particles of carbon, 
but other chromophore particles that absorb light and do not form toxic 
byproducts when pyrolyzed in hair ducts can also be used, and their use is 
specifically contemplated to be within the scope of this invention. One 
skilled in the art will appreciate that, if the heat of vaporization and 
absorption coefficient of a chromophore is known, thermodynamic principles 
can be used as illustrated herein to calculate what size range of 
particles will vaporize, and what size range will heat up and transfer 
heat to surrounding tissue without the loss of energy associated with 
vaporization of the particles. 
The invention is more particularly described with reference to carbon 
particles as follows. In a hair follicle, carbon particles with an average 
diameter of approximately 1.0 micron will vaporize when illuminated via a 
Nd:YAG laser having a light beam with an energy density of about 2.5 
J/cm.sup.2, and a pulse duration of about 10 nanoseconds. These explosions 
translate mechanical energy to kinetic energy in the form of a shockwave, 
which causes both heat and motion. It has been discovered that the 
shockwave caused by exploding chromophore particles contributes 
substantially to the damage to the skin tissue that feeds growing hair 
follicles. Thus, an important aspect of the present invention is selection 
of chromophores having a particle size that will readily explode under the 
type of illumination provided, i.e., the energy density of individual 
pulses and the length of the pulse duration. 
By contrast, relatively smaller particles of chromophore illuminated by 
pulses of light at the same power and pulse duration will tend not to 
explode, but will rapidly release the heat they absorb to a surrounding 
medium by thermal conduction. When the relatively smaller particles are 
confined within a hair duct, heat is rapidly conducted from the heated 
particles to the surrounding skin tissue, thereby causing thermal damage 
to such tissue. The thermal effects of illuminating the smaller particles 
may be increased by prolonging the pulse duration of the laser to the 
microsecond or millisecond range. For instance carbon particles with an 
average diameter in the range from about 1 to 50 nanometers will transfer 
absorbed heat to a surrounding medium such as skin tissue, substantially 
without explosion or vaporization when illuminated under the same 
conditions that explode 1 micron particles (i.e., a Nd:YAG laser with a 
fluence of about 2.5 J/cm.sup.2 and a pulse duration of about 10 ns). 
FIGS. 20A-C illustrate these concepts schematically. FIG. 20A schematically 
represents the transfer of photothermal energy to tissue surrounding a 
hair follicle 31 infiltrated with contaminant 14 containing carbon 
particles with diameters in the 1.0 to 50 nanometer range and illuminated 
by Nd:YAG laser light beam 7. FIG. 20B schematically represents the 
transfer of photomechanical energy to tissue surrounding a hair follicle 
31 infiltrated with contaminant 14 containing carbon particles with 
diameters of about 1.0 micron and illuminated by Nd:YAG laser light beam 
7. FIG. 20C schematically represents the combined transfer of 
photomechanical and photothermal energy to tissue surrounding a hair 
follicle 31 infiltrated with a combination of the contaminant carbon 
particles of FIGS. 20A and 20B. 
Due to the extraordinary amount of energy that is consumed in transforming 
solid particles to a gaseous state, vaporization of particles consumes a 
large portion of the energy delivered to the particles. By comparison, 
heating the particles is very energy efficient. For example, about 7,686 J 
per gram will heat graphite from 0.degree. C. to 3700.degree. C., its 
vaporization temperature, but about 10 times as much energy is required to 
vaporize graphite, or about 65,000 J per gram. Therefore, much more 
powerful light pulses are needed to vaporize graphite and utilize 
photomechanical damage than is required for a purely thermal effect. 
Vaporization of the chromophore particles is particularly useful for 
generating a force to propel the particles and their fragments deep into 
hair ducts and the walls of hair follicles. Once propelled into the 
vicinity of hair papillae, continued explosion of the particles by the 
pulses of light will produce shock waves and rapidly propel fragments so 
as to cause damage to hair growth cells responsible for the production of 
hair shafts. The damage inflicted on hair growth cells by these 
photomechanical effects may extend hundreds of microns into the walls of 
follicles. 
In one embodiment of the laser hair removal method, vaporization of the 
carbon particles is required to generate a force propelling the particles 
and their fragments deep into hair ducts and the walls of hair follicles. 
Once located in the vicinity of the hair papilla and the structures 
responsible for production of the hair shaft (hair growth cells), the 
particles can be exploded again and again by the laser pulses to produce 
shock waves and rapidly moving fragments that will damage surrounding 
tissue. The damage to surrounding tissue by these photomechanical effects 
may extend hundreds of microns into the walls of the follicles. The 
acoustic shock waves being transmitted at the speed of sound will 
propagate substantially deeper and faster than the thermal damage at the 
short 10 ns pulse duration. Once shattered by explosion, large particles 
and aggregates will end up as a collection of much smaller fragments, 
which will absorb light energy and transfer heat into tissue without much 
mechanical damage. 
In order to thermally devitalize cells in tissue surrounding a hair 
follicle, the tissue needs to be maintained at a high temperature for a 
period of time that varies with the temperature. The higher the 
temperature, the shorter the period required. For example, at 45.degree. 
C., the required duration is about a couple of hours. However, it takes 
only about 0.1 second to damage skin cells at 70.degree. C., and only 
about 1 millisecond at 80.degree. C. The temperature to which a 
chromophore particle will be raised by any given pulse duration and laser 
fluence as well as the amount of heat it will deliver to surrounding 
tissue depends upon the thermodynamic properties of the chromophore, and 
the size of the chromophore particle irradiated. 
The combination of mechanical and thermal energy transferred from the 
particles to the skin tissue sought to be destroyed is a very effective 
technique for achieving long term inhibition of the growth of hairs in 
hair ducts. Simultaneous photothermal and photomechanical damage to hair 
follicles is obtained by infiltrating into hair follicles a contaminant 
that contains a mixture of two particle sizes. For example, a contaminant 
containing a mixture of carbon particles having a diameter of about 1 nm 
to about 50 nm, for example about 10 nm, and carbon particles having a 
diameter of about 3000 nm to about 500 nm, for example about 1000 nm, can 
be used to induce simultaneous mechanical and thermal damage to skin 
tissue surrounding hair ducts. 
The contaminant can further include a liquid, such as an oil, surfactant, 
or water-based lotion. In all mixtures and/or suspensions of chromophore 
particles in a suitable liquid, as well as solutions in which the carbon, 
or other chromophore, particles are dissolved in a solvent, the liquid 
acts as a heat sink for a vaporized particle, and causes the vaporized 
particle to condense back into the solid phase with the release of its 
heat of sublimation. For example, at a dilution of less than 1% by volume 
of 1 micron sized carbon particles in oil, the particles may shatter and 
vaporize to gaseous carbon, as well as emit smaller carbon particles. The 
oil is correspondingly heated, and transfers its heat to nearby cells. 
Therefore, an oil-containing contaminant with concentrations of carbon 
particles less than about 20% by volume (such as 2, 0.2 or even 0.02 
volume %) increases the proportion of photothermal damage to the skin 
cells surrounding hair ducts, at the expense of photomechanical damage 
that would otherwise be caused by the particles alone. Also, rapidly 
moving solid carbon particles tend to be slowed down by the oil, thus 
lessening or preventing mechanical damage. Therefore, the proportion of 
mechanical to thermal damage caused in the hair follicles can also be 
controlled by varying the overall concentration or amount of the 
chromophore particles in the contaminant. For any given chromophore 
particle size and laser pulse width, there will be an optimum 
concentration of the light-absorbing chromophore in the mixture. Too much 
chromophore content (e.g., carbon particles) will act as a heat sink as 
well as block the passage of photons. Too little chromophore content will 
not absorb enough light, and will not heat up enough to effectively damage 
adjacent cells. 
In the case of a contaminant having chromophore particles with a 
substantial range of sizes (as is obtained by grinding large particles to 
obtain smaller particles), the proportion of photomechanical to 
photothermal damage caused to the skin cells surrounding the hair ducts by 
the particles infiltrated therein can be controlled by controlling the 
size distribution of the particles and/or the average size of the 
particles. In general, decreasing the average size of the particles, 
decreases the proportion of photomechanical to photothermal damage, and 
increasing the average size of the particles increases the proportion of 
photomechanical to photothermal damage. Similarly, when the distribution 
of particles having a range of sizes is skewed towards the relatively 
larger particles, a larger proportion of mechanical damage will be 
obtained than when the distribution is skewed towards the relatively 
smaller particles. 
In one embodiment of the invention, the particles infiltrated into hair 
ducts have a varied major dimension selected so that a combination of 
photomechanical and photothermal damage can be simultaneously administered 
to skin tissue adjacent to the hair duct, even when the pulse duration and 
the fluence of the pulses of light are held constant. It is generally 
desirable that no more than about 20 to about 5 percent of the energy 
delivered by the light source should be expended in vaporization of 
particles. Therefore, in one embodiment of the invention, wherein carbon 
is the chromophore, from about 10 to about 30 percent by weight of the 
particles have a major dimension in the size range from about 3000 nm to 
500 nm, and the balance of the particles have a major dimension in the 
size range from about 500 nm to 100 nm. Similarly, by proper selection of 
the proportion of the particles that fall into the smaller and the larger 
size ranges, the proportion of photomechanical to photothermal damage 
caused upon illumination of the particles at any fixed fluence can be 
controlled. 
The hair removal procedure may also be divided into two or more phases, 
including a first phase during which the contaminant is irradiated so as 
to explode the particles to drive them into the depths of the hair 
follicles, (i.e., the propulsion phase) and a second phase during which 
the contaminant is irradiated so as to raise the temperature of the tissue 
immediately surrounding the hair follicles to cause sufficient damage to 
inhibit future hair growth (i.e., the thermal phase). Such a procedure is 
described in co-pending U.S. Pat. application Ser. No. 08/644,231, filed 
May 13, 1996, which is incorporated herein in its entirety. For use in a 
multi-phase hair removal procedure of this type, during the first phase a 
majority of the carbon particles have an average diameter in the range 
from about 1 to about 60 nanometers, for example, about 10 nm, to maximize 
the proportion of photothermal damage effected. Then, during the second 
phase of the illumination, to maximize the proportion of photomechanical 
damage caused by illumination of the particles, the majority of the 
particles have an average diameter in the range from about 3000 nm to 500 
nm, for example about 1000 nm. These size ranges are particularly 
preferred when the chromophore particles are carbon and the illumination 
is by pulses of light about 10 nanoseconds in duration with a wavelength 
of about 1.06 micron. One skilled in the art will be able to adjust the 
size ranges to correspond to alternative chromophores, wavelengths of 
light, and pulse length using thermodynamic calculations. 
The present invention provides improvements in known methods of laser hair 
removal procedures. It allows the practitioner to control the thermal 
and/or mechanical damage administered to hair follicles either 
simultaneously or in sequential phases, by selection of the size of 
particles in a contaminant infiltrated into hair ducts. The practitioner 
is afforded increased control over the difficult task of forcing 
chromophore particles into the depths of hair ducts using laser light. The 
invention also affords the practitioner improved control over the amount 
of heat that is administered to the tissue in and surrounding the hair 
follicles during lasing. As a result of these improvements, the risk of 
unwanted damage to skin tissue is lessened, while the techniques of 
inhibiting hair growth are improved. 
No. 7: A Method for Controlling Photomechanical Versus Photothermal Damage 
During Laser Hair Removal by Selecting Pulse Duration 
The use of a laser to induce hair follicle damage via irradiation of a 
carbon chromophore (e.g., carbon particles) has been previously described. 
The purpose of this invention is to employ modulation of and/or 
combinations of laser pulse durations to control administration of 
photomechanical and/or photothermal damage to the hair cells via an 
exogenous chromophore infiltrated into hair ducts. 
The effect of particle size in controlling whether photomechanical or 
photothermal damage is administered to hair follicles by means of 
chromophore particles infiltrated therein is disclosed in Section No. 6 
above. It is also possible to achieve a combination of mechanical and 
thermal damage to tissue surrounding hair ducts by using a relatively 
homogeneous size of particles, in conjunction with a combination of 
relatively long and short pulses of light. In general, short pulses of 
light tend to explode a chromophore particle, thus causing photomechanical 
damage. Pulses having a pulse width longer than the thermal relaxation 
time of a particle tend to heat up a particle without explosion so that 
heat is transferred to a surrounding medium. The surrounding medium is 
skin tissue surrounding a hair duct and/or a liquid medium in which the 
particle is dissolved or suspended. Thus, photothermal damage is caused to 
tissues adjacent to chromophore particles radiated by relatively long 
pulses of light. The combination of long and short pulses can be an 
alternating pattern of long and short pulses, a succession of short pulses 
followed by a succession of long pulses, or vice versa, or the long and 
short pulses can be administered simultaneously. In the latter case, it 
may be convenient to utilize two lasers simultaneously. 
As used herein, the terms "long" and "short" are relative terms and must be 
defined with reference to the type and size of the chromophore particles 
illuminated. This principle is illustrated herein with reference to carbon 
particles and light pulses provided by a Nd:YAG laser with pulse frequency 
of about 10 Hz and fluence of about 2 to about 3 J/cm.sup.2. Under these 
conditions, a "short" pulse duration (of a Nd:YAG laser) will be from 
about 10 ns to about 30 ns, while a "long" pulse duration will be from 
about 100 .mu.s to about 100 ms. Preferably the carbon particles are 
suspended in an oil or water medium. Irradiation of the carbon with a 
"short" pulse will: a) break up aggregates of carbon particles, b) induce 
shattering of the larger (&gt;50 nm) particles into smaller particles, c) 
drive particles deeper into the hair shaft due to the explosive force of 
the shattering of particles, and d) cause vaporization of the carbon to 
induce photomechanical tissue damage. A "long" pulse, on the other hand, 
will lead to heating of the smaller carbon particles, and the heat will be 
transferred (e.g., via an oil medium) to the surrounding tissue to induce 
photothermal damage, but will substantially avoid exploding or vaporizing 
the particles. 
One option for producing both photothermal and photomechanical damage to 
the follicular tissue is to alternate short and long pulse durations when 
illuminating chromophore particles infiltrated into hair ducts. 
Alternating the pulse duration between short and long pulses will serve to 
break up any aggregates of carbon particles, and will cause both 
photomechanical and photothermal damage to tissue surrounding hair ducts 
into which the particles have been infiltrated. 
The following examples model a zero-order estimation of the laser 
parameters suitable for administering any desired combination of 
photomechanical and photothermal thermal damage to hair follicles without 
burning skin, coagulating blood vessels in the dermal matrix, or 
destroying the skin pigment (i.e. melanin) located at the interface of 
epidermis and dermis. 
EXAMPLE 4 
Short vs. Long Pulse Lasers 
The laser pulse energy and duration give rise respectively to the amount 
and rate of energy absorbed in light-absorbing chromophores respectively. 
For a given energy, the shorter the pulse duration, the higher the 
temperature rise in the light-absorbing medium. The absorbed energy is 
confined well inside the light absorbing chromophore at the end of a short 
duration pulse. Conversely, much of the heat may be dissipated into the 
surrounding medium if the pulse duration is very long. As a zero-order 
approximation, the energy dissipation distance in a given period of time 
can be written as: 
EQU x=.sqroot..alpha..tau. (1) 
where x in cm is the energy dissipation distance; .tau. in seconds is the 
duration of energy dissipation; .alpha. in cm.sup.2 /sec is the thermal 
diffusivity, which is determined by the mathematic expression .alpha.=K/pc 
in which K is in J cm.sup.-1 s.sup.-1 .degree.C.sup.-1, p is in 
g/cm.sup.3, and c is in Jg.sup.-1 .degree.C.sup.-1, represent the thermal 
conductivity, density, and thermal capacity, respectively. Table 4 lists 
the energy dissipation distances in graphite, mineral oil, and skin during 
a period of 10 ns (typical Q-switched Nd:YAG laser pulse duration), 100 
.mu.s (typical duration of non-Q-switched or free running Nd:YAG laser), 
and 100 ms (the duration between pulses of a 10 HZ laser). Table 4 shows 
that for a 1 .mu.m graphite particle suspended in mineral oil or a 1 .mu.m 
melanosome in skin, the absorbed energy is confined well inside the 
particle at the end of a 10 "short" ns pulse, but dissipates a significant 
distance from the particle during a "long" 100 .mu.s pulse. 
TABLE 4 
______________________________________ 
The energy dissipation distance X (.mu.m) in graphite, mineral oil, & 
skin during period .tau. 
.tau. X.sub.GRAPHITE 
X.sub.OIL 
X.sub.SKIN 
______________________________________ 
10 ns 0.16 0.03 0.03 
100 .mu.s 
16.3 2.82 
3.23 
l00 ms 515 89.1 
102 
______________________________________ 
Note: 
the thermal dffusivities (cm.sup.2 s.sup.-1) used in the calculation for 
graphite, mineral oil, and skin are 0.027, 7.94 .times. 10.sup.-4, and 
0.001, respectively 
Neglecting the energy loss due to dissipation, the instantaneous 
temperature rise in a light absorbing medium at the end of a 10 ns laser 
illumination can be expressed as 
##EQU1## 
where .mu..sub.a in cm.sup.-1 is the absorption coefficient; and .phi.in 
J/cm.sup.2 is the laser fluence. Because of the high absorption 
coefficient of graphite, its instantaneous temperature rise is over 
1000.degree. C. even at a 0.1 J/cm.sup.2 laser fluence. The vaporization 
temperature of graphite (about 3700.degree. C.) is reached at about 0.3 
J/cm.sup.2. For purposes of thermal coagulation of the hair follicle, 
vaporization of light absorbers should be avoided. It takes about 7,686 J 
per gram to heat graphite from 0.degree. C. to 3700.degree. C., but it 
needs about 9 to 10 times more energy to vaporize graphite (about 65,000J 
per gram). It is estimated that only about 5% of the energy needed to 
vaporize graphite is converted into kinetic energy of the vapor. Thus, 
about 95% of the laser energy cannot be used to raise the temperature of 
the tissue to be thermally damaged. Therefore, a Q-switched short pulse 
laser is not a good choice in terms of thermal damage of tissue. For 
graphite particles whose size is small enough so that the energy 
dissipation is significant even during a 10 ns pulse duration, 
vaporization of these particles can be prevented as was demonstrated for 
the situation of 1 nm and 10 nm graphite particles suspended in mineral 
oil. However, this scenario is hard to be implemented in practice because 
small particles tend to group together. For example, while a single 
C.sub.60 fullerene is only about 1 nm in diameter, the aggregates of 
C.sub.60 fullerene can be as large as 300 .mu.m across. Furthermore, 
longer pulse duration is required in order to prevent burning of the skin, 
damaging blood vessels, destroying the skin pigmentation, i.e., the 
melanosomes. 
For pulse durations longer than 100 .mu.s, the energy deposited in a light 
absorbing chromophore can spread out significantly and thus reduce the 
peak temperature rise of the chromophore. As shown in Table 4, during a 
100 .mu.s period, the energy spreads out about 16 .mu.m in graphite and 
about 3 .mu.m in mineral oil. With respect to the photon penetration depth 
of about 0.1 .mu.m in graphite at 1064 nm, the absorbed energy dissipates 
very far away from the source. For 1 .mu.m graphite particles suspended in 
mineral oil, the temperature rise of the particle at the end of 100 .mu.s 
illumination period with 1 J/cm.sup.2 fluence is about 450.degree. C. At 
the same fluence, the instantaneous temperature rise without energy 
dissipation would be over 10,000.degree. C. if vaporization did not take 
place. A long pulse laser is clearly the choice to effect thermal damage 
of hair follicles. Even a 100 .mu.s pulse is not long enough for some 
situations, as demonstrated below. 
EXAMPLE 5 
Thermal "Heating" of Hair Follicle with Long Pulse Laser 
The temperature rise in the light absorbing chromophore and the surrounding 
medium can be obtained by solving the heat conduction equation: 
##EQU2## 
where the first term is the energy flow rate into a unit volume due to a 
temperature gradient with K representing thermal conductivity; the second 
term represents the energy production rate per unit volume by heat source; 
and the term on the right side of the equation represents the energy 
associated with the temperature change per unit volume per unit time. With 
boundary and initial conditions given, the above equation can be solved to 
give the temporal and spatial distribution of temperature. 
For the case of a hair follicle filled with light absorbing chromophores, 
analytical expressions of the temperature inside the hair follicle and in 
the surrounding tissue can be obtained with the following approximations 
(H. S. Carslaw et al, Conduction of Heat in Solids, Oxford University 
Press, N.Y., 1995, p 347): 
The hair follicle is considered as an infinitely long cylinder. 
The light absorbing medium inside the follicle and the surrounding tissue 
are different uniform substances, but with the same initial temperature 
T.sub.0. 
There is a constant heat production S per unit time per unit volume at t&gt;0 
inside the cylinder. 
The temperature rise during heating and thermal relaxation after heating 
are related by: 
##EQU3## 
where .DELTA.T1(r, t) and .DELTA.T(r, t) represent the temperature change 
during and after the heating phase, respectively; .tau..sub.p is the 
duration of heating; and r and t denote the radial coordinate and time, 
respectively. The thermal conductivities and diffusivities of the two 
media inside and outside the cylinder need to be known in order to 
calculate the temperature change for hair follicles filled with a 
topically applied contaminant comprising micron size graphite particles 
suspended in mineral oil with a mass ratio of 20%. These quantities in the 
contaminant are determined by the properties of graphite, mineral oil, and 
their volumetric ratio, using known procedures. 
For heating of a graphite suspension in mineral oil with laser pulse longer 
than 100 .mu.s, it is possible to heat up the lotion fairly uniformly 
because of the energy dissipation from graphite particles to mineral oil. 
Assuming a constant laser fluence reaching a hair follicle and absorption 
in the follicles of all the photons striking it, the heat production per 
unit volume per unit time is determined by formula 1.5 as follows: 
##EQU4## 
where S (Jcm.sup.-3 s.sup.-1) is the heat production per unit volume per 
unit time; .phi.(J/cm.sup.2) is the laser fluence striking the hair 
follicle; a (cm) represents the radius of the hair follicle; and 
.tau..sub.p (sec) denotes the pulse duration. 
With the treatments discussed above, the temperature distribution T(r,t) 
for the case of a hair follicle filled with graphite/oil contaminant are 
calculated for different laser fluences and pulse durations. Immediately 
after the laser pulse, the energy is localized well inside the hair 
follicle, but the temperature of the lotion is well below the vaporization 
temperature of graphite (about 3700.degree. C.). By 10 ms after 
irradiation, the hair follicle is appreciably thermally relaxed. To 
demonstrate the pulse duration effect, the laser fluence is kept at 3 
J/cm.sup.2, but the pulse duration is stretched from 100 .mu.s to 10 ms. 
For pulse durations from 100 .mu.s to 10 ms, the temperature rise of the 
tissue between the wall of a follicle and a distance one follicle radius 
away from the wall is over 50.degree. C. for a period of a few 
milliseconds. The corresponding absolute temperature is over 80.degree. C. 
after adding on the base body temperature (about 37.degree. C.). 
Tissue is damaged if kept at 80.degree. C. for a period of about 1 ms. 
Thus, the tissue as far as one hair follicle radius away from the hair 
duct wall is thermally damaged, with transfer of sufficient heat to 
prevent hair growth from the follicle for a long period. When the same 
amount of energy is delivered in a pulse of 100 ms, the temperature rise 
of the tissue one follicle radius away from the follicle wall is not 
enough to thermally damage the tissue. However when the fluence is raised 
from 3 J/cm.sup.2 to 6 J/cm.sup.2 for the 100 ms pulse, the temperature 
rise in the tissue between the wall of a follicle and one follicle radius 
away from the wall is over 30.degree. C. for a period of about 0.1. The 
corresponding absolute temperature distribution is about 70.degree. C. for 
a period of about 0.1 second, which is high enough to cause thermal damage 
of the tissue. By these studies it is discovered that when the pulse 
duration gets longer, the absorbed energy is more uniformly distributed 
over the tissue. By the time a pulse duration as long as 1 sec is reached, 
selective thermal damage of the tissue immediately surrounding a hair 
follicle is almost impossible. Thus, from the point of view of selectively 
damaging the tissue near a hair follicle, a shorter pulse is preferred. 
However, as a general rule, the shorter the pulse duration, the greater 
the danger of causing undesirable destruction of skin. 
The invention thus provides improvements in known methods of laser hair 
removal procedures. It allows the practitioner to control the thermal 
and/or mechanical damage administered to hair follicles either 
simultaneously or in sequential phases, by selection of the size of 
particles in a contaminant infiltrated into hair ducts. The invention 
provides to the practitioner increased control over the difficult task of 
forcing chromophore particles into the depths of hair ducts using laser 
light. The invention also affords the practitioner improved control over 
the amount of heat that is administered to the tissue in and surrounding 
the hair follicles during lasing. As a result of these improvements, the 
risk of unwanted damage to skin tissue is lessened, while the techniques 
of inhibiting hair growth are improved. 
No. 8: A Method for Sunlight-Assisted Hair Removal 
Methods of hair removal are known in which a photochemical is infiltrated 
into hair ducts and then exposed to light having a wavelength absorbed by 
the contaminant. Upon illumination, the photochemical produces a chemical 
species that destroys skin tissue in and around the infiltrated hair 
ducts. For example, Japanese patent No. 63-249577 discloses methods of 
hair removal that utilize porphyrin and chlorin derivatives, which release 
singlet oxygen upon irradiation by a frequency-matched light. However, 
known methods are time consuming and are generally administered in a salon 
or clinic, making them expensive. 
The present invention overcomes some of the difficulties of the art by 
utilizing sunlight as the light source in a method for long term 
inhibition of hair growth. This method of inhibiting hair growth can be 
practiced without any specialized equipment or skills. In this invention, 
the photochemical is a prodrug that is activated by sunlight to create a 
chemical species toxic to cells in and surrounding hair ducts that cause 
hair growth, but is safe for topical application to the surface of skin. 
Non-limiting examples of sunlight-activated prodrugs that can be used in 
the practice of this invention are photophrine II, amino levulenic acid, 
beta carotene and tetracycline. 
The sunlight-activated photochemicals are administered at a relatively high 
dosage, for example about 2% by weight of a aqueous solution. However, it 
should be noted that a substantially more dilute concentration (for 
example, one ten times less concentrated that what is used to cause hair 
removal) will not cause hair removal, but will cause a slight inflammation 
in the hair follicles sufficient to stimulate hair growth. 
In the method of the invention, the sunlight-activated photochemical is 
applied to the skin surface in an area in which it is desired to inhibit 
hair growth. Gentle massage is used to infiltrate a portion of the 
photochemical into hair ducts in the section of skin treated. Due to the 
extremely high metabolic rate of hair growth cells, the sunlight activated 
prodrug is preferentially and rapidly absorbed within hair ducts and into 
cells and adjacent tissue structures that generate hair growth. Such cells 
include hair papilla cells, stem cells, keratinocytes, and endothelial 
blood vessels. Absorption of the photochemical into other, more slowly 
growing cells, is at a substantially slower rate. In addition, the stratum 
corneum layer in skin acts as a protective barrier to prevent significant 
absorption of the photochemical through the skin surface. 
A period of time must be allowed for the photochemical to be absorbed by 
and concentrated in the target hair growth cells. Generally, a period of 
about 1 to about 7 hours is sufficient time to allow normal biological 
processes to assist in absorption of the photochemical in the fast-growing 
target cells. The rest period for any particular photochemical can be 
determined empirically by one skilled in the art. After this rest period, 
the contaminated skin section is exposed to direct sunlight for a period 
of time sufficient to activate the prodrug, thereby causing damage to the 
hair growth cells. Generally, the time of exposure will be from about 
three to about four hours, but may in some cases be as little as 20 
minutes. 
Therefore, in one embodiment of the invention, the sunlight-activated 
photochemical is applied to the skin surface before retiring to bed, and 
the next morning the area of skin so treated is exposed to direct sunlight 
by taking a sun bath or going to the beach for a period of several hours. 
By timing the illumination in this manner, the hair-producing cells in the 
follicle, as well as the tissue immediately surrounding the follicle that 
feed the hair, are damaged by photochemical activation of the prodrug 
photosensitizer, but without substantial damage to other tissue. 
In another embodiment of the invention, the photochemical is entrapped or 
encapsulated within microcarrier particles in a formulation suitable for 
topical administration, such as a formulation of liposomes or coacervate 
microcapsules. FIGS. 21A-E show different types of microcarriers 
containing a photochemical. As shown in FIG. 22, the microcarrier 
particles 20 containing the photochemical are applied topically to the 
skin surface 12 and induced to penetrate into a hair duct 31 in the spaces 
around hair shaft 33, for example by gentle massage of the skin surface. 
An ultrasound vibrator 18 may be applied to the skin surface 12 to force 
the microcarrier particles 20 into the hair duct 31 as shown in FIG. 23. 
The lining of hair ducts does not have an epithelial barrier layer, such as 
the stratum corneum. Consequently, the lipids in lipid-based particles, 
such as liposomes, enhance penetration of the prodrug across the cell 
walls of papilla cells, stem cells, and keratinocytes in the infiltrated 
hair ducts. Then, irradiation of the skin surface with sunlight as 
described above activates the photochemical prodrug so as to damage these 
hair growth cells. 
To accommodate this function, the microcarrier particles are sized large 
enough to avoid absorption across the stratum corneum at the skin surface, 
but small enough for entry and passage into the hair duct. For application 
to humans, the diameter of the microcarrier particles is generally less 
than about 70 .mu.m, for example about 10 .mu.m to about 50 .mu.m because 
the diameter of hair ducts in humans is in the size range from about 70 
.mu.m to about 1 micron. 
Methods are well known for encapsulating an active agent within a 
microcarrier particle, such as a liposome or a microcapsule. For example, 
there are at least three types of liposomes. Multivesicular liposomes 
(MVL) are man-made, microscopic lipid vesicles comprising lipid membranes 
enclosing multiple non-concentric aqueous chambers. Multilamellar 
liposomes or vesicles (MLV) have multiple "onion-skin" concentric 
membranes, in between which are shell-like concentric aqueous 
compartments. Multilamellar liposomes and multivesicular liposomes 
characteristically have length-weighted mean diameters in the micrometer 
range, usually from 0.5 to 25 .mu.m. Unilamellar liposomes or vesicles 
(ULV) are liposomal structures having a single aqueous chamber, usually 
with a mean diameter range from about 20 to 500 nm. 
Multilamellar and unilamellar liposomes can be made by several relatively 
simple methods. The prior art describes a number of techniques for 
producing ULV and MLV (for example U.S. Pat. Nos. 4,522,803 to Lenk; 
4,310,506 to Baldeschweiler; 4,235,871 to Papahadjopoulos; 4,224,179 to 
Schneider; 4,078,052 to Papahadjopoulos; 4,394,372 to Taylor; 4,308,166 to 
Marchetti; 4,485,054 to Mezei; and 4,508,703 to Redziniak). Methods for 
making multivesicular liposomes are disclosed in Kim et al., Biochem. 
Biophys. Acta, 728:339-348, 1983). For a comprehensive review of various 
methods of ULV and MLV preparation, refer to Szoka, et al. Ann. Rev. 
Biophys. Bioeng. 9:465-508, 1980. 
Also contemplated within the scope of this invention is a composition for 
topical application to a skin surface for inhibiting hair growth on the 
skin surface. The composition comprises a sunlight-activated prodrug 
encapsulated in a microcarrier particle, such as a liposome or 
microsphere. The diameter of the particles is generally less than 70 
.mu.m, for example about 10 .mu.m to about 50 .mu.m. In one embodiment, 
the sunlight activated prodrug is selected from the group consisting of 
photophrine II, amino levulenic acid, and tetracycline. The composition 
further comprises a physiologically acceptable carrier suitable for 
topical application. The carrier may comprise any conventional topical 
formulation base, such as those described in Remington's "Pharmaceutical 
Sciences," 17th Edition (Mack Publishing Co., Pa.), the disclosure of 
which is incorporated by reference. A lotion, suspension in oil, solution, 
cream, ointment, gel, aerosol, or nebulized formulation are representative 
of the topical compositions of this invention. 
This method for inhibiting the growth of unwanted hair provides the 
advantage of home treatment because the light source used to activate the 
photochemical prodrug is sunlight. A topical composition containing the 
sunlight-activated prodrug can be self-administered, and, after a rest 
period to allow accumulation of the prodrug in hair-growth cells lining 
hair ducts, a simple sun bath is all that is required to activate the 
prodrug and thereby inflict sufficient damage to inhibit hair growth on a 
long term basis. 
No. 9: A Method for Inhibiting Hair Growth Using Anti-Proliferative Agents 
It is known to infiltrate photoactivated chemical compounds, such as 
porphyrin and chlorin derivatives, into hair ducts, and then to illuminate 
them with light at a wavelength that causes the photochemicals to release 
species harmful to cells in hair follicles responsible for hair growth. 
However, the light sources used for illumination, such as lasers, are 
expensive and usually require trained operators to avoid unwanted damage 
to skin and eyes. 
The present invention provides a method for temporarily inhibiting growth 
of unwanted hair on a section of skin by topically applying an 
anti-proliferative agent to the section of skin to be treated. The 
anti-proliferative agents do not require activation by any type of light 
source. Normal hair growth will recommence once the treatment is 
withdrawn. 
During application of the anti-proliferative agent, care is taken to assure 
that at least a portion of the anti-proliferative agent is delivered into 
hair ducts on the section of skin to be treated to inhibit hair growth. 
Preferably the anti-proliferative agent is delivered along the full length 
of the hair duct, which length varies depending upon the bodily location 
of the skin section to be treated (i.e., on the face, legs, or arms). The 
depth of the hair duct also varies for an individual hair depending upon 
the phase of the hair growth cycle in which it is found. During the mature 
anagen phase, for example anagen V and VI, the hair follicle is fully 
extended (to a depth of 3.0 to about 5.0 mm), and the distance to the 
bottom of the follicle from the skin surface is about twice that during 
the telogen phase of the hair growth cycle. Therefore it is advantageous 
to synchronize the growth cycle of the hairs to be treated before 
application of the anti-proliferative agent to the area to be treated for 
inhibition of hair growth. Methods for synchronizing the hair growth cycle 
are disclosed above in Section No. 1 herein. 
The anti-proliferative agent is applied to the skin surface in any suitable 
topical formulation, such as a lotion, cream or gel. Suitable formulations 
preferably are designed to aid in delivery of the anti-proliferative agent 
into hair ducts, and may therefore, include one or more chemical agents 
that will reduce surface tension, such as a surfactant. 
Anti-proliferative agents useful in the practice of this invention include 
small molecules as well as macromolecules, such as proteins or enzymes, 
that interfere with or interrupt in any way the cycle of cell 
proliferation. Representative examples of anti-proliferative agents useful 
in the compositions and methods of the present invention include 
methotrexate, doxorubicin, taxol, tumor necrosis factor, chlorambucil, 
interleukins, etoposide, cytarabine, fluorouracil, vinblastine. The 
mechanism of action of the anti-proliferative agent is immaterial other 
than that it interferes with or interrupts the cycle of cell 
proliferation. For example, methotrexate, aminopterin and cytosine 
arabinoside (also known as cytarabine and Ara-C) are cell cycle-specific 
antimetabolites that kill cells only when they are synthesizing DNA. 
Fluorouracil inhibits formation of both DNA and RNA. Methioninease is an 
enzyme that inhibits uptake of methionine by hair papilla cells 
proliferating at a high rate. 
Hair ducts are not lined by an epithelial barrier layer, such as the 
stratum corneum, but do contain rapidly proliferating hair papilla cells, 
stem cells, keratinocytes, and endothelial blood vessels, which generate 
hair growth. These cells in the hair duct responsible for hair growth are 
the fastest growing cells in the body, aside from tumor cells. Due to the 
absence of a barrier layer in the hair duct, the anti-proliferative agents 
are preferentially take up by these hair growth cells, which have a high 
metabolic rate. Entry of the anti-proliferative agents into other, more 
slowly growing cells, is at a substantially slower rate. Consequently, the 
anti-proliferative agents are preferentially absorbed into the target hair 
growth cells, with the result that hair growth is inhibited. 
Application of the anti-proliferative agent to the skin surface is repeated 
at spaced intervals of hours or days until hair growth is inhibited. 
Generally, the anti-proliferative agent is applied two times daily for so 
long as it is desired to inhibit the growth of hairs from the treated 
portion of the skin. Once treatment is stopped, hairs in the treated 
section of skin will commence a normal growth pattern. 
In one embodiment, the anti-proliferative agents are encapsulated in 
lipid-based particles, such as liposomes or microcapsules, for application 
to the skin surface. The lipid-based particles are sized small enough to 
enter into hair ducts in the section of skin, but large enough not to be 
absorbed across the stratum corneum. Care is taken during application of 
the lipid-based particles to assure that at least a portion of the 
drug-bearing particles enters into the hair ducts. For example, the micro 
particles can be formulated in a physiologically acceptable carrier 
containing one or more chemical agents that will aid entry of the 
particles into hair ducts. It is believed that administration of the 
anti-proliferative agents encapsulated in lipid-based particles will 
increase uptake of the anti-proliferative agent. As the lipid-based 
particles begin to break down in the hair duct, both the encapsulated drug 
and lipids from the bilayers of the lipid-based particles are released. 
These lipid byproducts can aid in delivery of the released drug across the 
cell membranes of the target cells. Methods for obtaining an active agent 
encapsulated in lipid particles, such as liposomes and microcapsules are 
well known in the art and are referred to above in Section No. 8 herein. 
Lipid-based particles, such as liposomes, deliver the encapsulated agent 
slowly within the hair duct, so that the cells lining the hair duct are 
bathed in the anti-proliferative agent over an extended period of time, 
generally over a period of hours or even days. Slow release of the 
anti-proliferative agent from the lipid-based particles is particularly 
advantageous for those agents that interfere with a particular step in the 
proliferation cycle of the cells, such as formation of DNA and/or RNA, 
because not all cells enter mitosis at the same time. 
The dose of the anti-proliferative agent administered, whether encapsulated 
or unencapsulated, can vary from about a few picomoles to about several 
hundred millimoles. The desirable dose of anti-proliferative agent per 
unit area of skin treated is a hair growth-inhibiting amount, and will 
vary depending upon such characteristics as the stage of target hairs in 
the hair growth cycle at the time of administration, the age and condition 
of the subject, the particular properties of the agent, and the dosage 
schedule. In general, the dosage range of the anti-proliferative agent 
appropriate for topical application to humans is in the range of about 
0.001 to about 6,000 mg/m.sup.2 of body surface area, generally applied in 
a cream, ointment or solution containing about 10% of the 
anti-proliferative agent by weight. While doses outside the foregoing dose 
range may be given, this range encompasses the breadth of use for most 
anti-proliferative agents useful for inhibiting hair growth. The dose 
range for a particular anti-proliferative agent can be easily ascertained 
as previously described. 
The present invention provides the advantage over other hair removal 
procedures that no specialized equipment is required to inhibit growth of 
unwanted hair. No lasers, razors, depilatory needles, etc., are required 
for safe and temporary inhibition of hair growth. The anti-proliferative 
agent is repeatedly applied onto the surface of skin so as to cause the 
anti-proliferative agent to enter hair ducts therein, and hair growth will 
recommence upon cessation of the treatment. The embodiment of the 
invention in which the anti-proliferative agent is administered in a slow 
release lipid-based formulation provides convenience by reducing the 
number of times the formulation must be used to accomplish the goal of 
inhibiting hair growth. 
No. 10: Use of Methionine to Stimulate Hair Growth or Regrowth 
Among many people, there is great interest in stimulating the growth or 
regrowth of human hair. For example, alopecia, especially male pattern 
baldness, is a condition that is common to a large proportion of the male 
population. The present invention provides a method for stimulating hair 
growth or regrowth to reduce the symptoms of hair loss. 
It is known that the amino acid methionine is required by the body for 
rapid cell proliferation, such as in the growth of tumors. The inventors 
herein have discovered that application of methionine to a skin section so 
that it penetrates into the hair ducts to contact hair growth cells 
therein can be used to induce growth of hairs from follicles therein. (The 
anagen stages of the hair growth cycle are characterized by rapid 
proliferation of hair growth cells). In some cases, even if growth of 
hairs from the target follicles has ceased for a considerable period of 
time, the administration of methionine into the hair ducts, so as to 
contact the hair growth cells, i.e., the hair stem cells, will restore 
hair growth. In other cases, vellum hairs have been restored to normal 
pigmented hair growth by the application of methionine to the hair growth 
cells in hair ducts. 
Methionine is administered to hair growth cells in a hair follicle in a 
hair growth stimulating amount, which may differ depending upon the phase 
in the hair growth cycle, the anatomical location of the hairs, such 
factors as the age and general health of the patient, and the dosage 
schedule. Taking these factors into account, one of skill in the art will 
be able to determine the appropriate timing and amount of doses 
appropriate for any individual in need of treatment. In general, however, 
it is recommended that a dose of about 0.001 to about 6,000 mg per square 
meter of skin surface to be treated should be rubbed into the skin section 
twice a day, for instance morning and night. As methionine is non-toxic to 
all mammals, there is no known overdose effect. 
The treatment should be continued until satisfactory hair growth has been 
restored. In some individuals restored or enhanced hair growth is noticed 
in as little as about 3 to about 5 weeks, while in others a noticeable 
difference in hair growth or regrowth is not noticed until the treatment 
has been continued for a period of several months, for example, 5 months. 
To enhance penetration of methionine into hair ducts and enhance uptake of 
the amino acid by hair growth cells therein, the methionine can be 
administered in a liposome or other lipid-based microparticle. The 
properties of liposomes and methods for encapsulating a biologically 
active agent, such as methionine, into liposomes are described in Section 
No. 8 herein. The methionine can also be contained in a formulation 
suitable for topical administration, such as an ointment, cream, 
suspension or solution. 
The present method of stimulating hair growth by contacting hair growth 
cells with sufficient methionine to stimulate hair growth cells in hair 
ducts has an advantage over prior art hair stimulation compounds and 
methods of their use in that methionine is not toxic to mammals. In 
addition, as it is an amino acid, Methionine is inexpensive to use in 
comparison with prior art hair growth stimulating drugs, such as 
Minoxidil. 
No. 11: A Method for Treating Herpes with Laser 
Seroepidemiologic studies have shown that infections of Herpes viruses are 
found worldwide. Infections of Herpes Simplex (oral or genital) or Herpes 
Zoster virus can manifest as skin lesions and/or rash at almost any 
location on the body. After a primary infection subsides, Herpes virus is 
reported to reside within the skin at the bulge area of the hair duct 
during latent phases of the disease. For this reason, mild trauma to the 
skin, or any treatment of the skin with a topical medication or lotion, 
can be followed by reactivation of the disease. It is known to treat such 
manifestations with an anti-viral agent that interferes with the 
replication of viral DNA, for example, oral administration of acylovir or 
a topical 5% acylovir ointment or cream. 
The present invention provides an alternative method for preventing Herpes 
outbreaks on the skin of susceptible individuals and/or treating 
infections of Herpes viruses on skin. During latency, Herpes viruses 
reside in the bulge area of the hair follicles. FIG. 1 shows a 
cross-section of a hair duct with a hair shaft 33, sebaceous gland 38, and 
bulge area 40. The hair growing in the hair duct shown in FIG. 1 is in the 
anagen phase of the hair cycle, so that the follicle is extended to its 
full length, and the bulge area 40 of the hair duct is located about 
one-half way down the follicle, just below the sebaceous gland. 
In this invention, reactivation of a Herpes virus infection in the form of 
skin lesions is prevented or treated. To prevent reactivation, hair ducts 
in the infected skin section are infiltrated with a light-absorbing 
contaminant so that at least a portion of the contaminant enters the bulge 
area of hair ducts containing latent Herpes viruses. Then the contaminated 
skin section is illuminated with short pulses of light at a wavelength 
more highly absorbed by the contaminant than by skin. Light energy 
absorbed in the form of heat or kinetic energy by the infiltrated 
contaminant in and around the bulge area is transferred to the latent 
viruses residing in the hair ducts. As a result, the Herpes viruses are 
denatured or destroyed, rather than suppressed in replication. By taking 
these steps, an outbreak of a Herpes skin infection is prevented. 
A Herpes skin infection can also be treated during an episode of 
reactivation using the method of this invention. During a reactivation of 
a Herpes skin infection, latent viral particles in hair ducts become 
active and multiply, with transmission of viral particles up through the 
hair duct to the skin surface. By practice of this invention during an 
episode of reactivation, viral particles throughout the hair duct are 
heated and destroyed. 
The methods of this invention are variations of laser hair removal 
techniques. It has now been discovered that these methods can be used to 
destroy or eradicate Herpes viruses sequestered within hair ducts in an 
infected skin section, whether or not the hair ducts contain viable hairs. 
U.S. Pat. Nos. 5,226,907 and 5,425,728 to Tankovich, which are 
incorporated herein in their entireties, disclose methods for hair removal 
and/or long term inhibition of hair growth utilizing a light absorbing 
contaminant that is infiltrated into hair ducts and then illuminated with 
short pulses of light. The contaminant is generally a water or oil-based 
suspension or solution containing chromophore particles having a good 
absorption at or near at least one frequency band of light, but any type 
of contaminant that absorbs light energy can be used. If the contaminant 
contains chromophore particles, for example carbon or graphite particles, 
they are generally sized too large to penetrate the barrier layer of the 
stratum corneum, but small enough to readily infiltrate the treated hair 
follicles. These techniques are modified in the present invention in that 
hair ducts containing latent viruses are infiltrated with the contaminant 
so that at least a portion of the contaminant enters the bulge area of the 
hair ducts adjacent to the latent viruses. Then the contaminated hair 
ducts are illuminated with short pulses of a light beam containing at 
least one wavelength that is well absorbed by the contaminant, but which 
penetrates skin with a minimum of absorption and scattering therein, such 
as that produced by a Nd:YAG laser. The short pulses of light can be used 
to cause explosions in the particles so as to drive the contaminant deep 
into the bulge area of hair follicles. The short pulses of light also 
cause heating of the contaminant. 
Heat generated in irradiated contaminant in and around the bulge area of 
hair ducts is transferred to viral particles either by conduction or by 
transfer of kinetic energy from explosion of particles in the contaminant. 
The short pulses of light may also destroy viral particles on a skin 
surface if the viral particles absorb the frequency of light used during 
the illumination, or if there is sufficient contaminant on the skin 
surface to absorb heat from the pulses of light. Generally, to destroy 
viruses in hair ducts, i.e., in the bulge area, the viral particles 
contained therein should be raised to a temperature of about 70.degree. C. 
to about 80.degree. C. for about 0.1 to 1.0 second. The size and material 
of the light absorbing chromophore particles in the contaminant should be 
matched to the properties of the light source so as to deliver sufficient 
heat to the bulge area of the infected skin section to provide the 
necessary heat to destroy the viral particles without substantial damage 
to the skin section treated. In general, the particles are sized large 
enough to avoid penetration of the particles through the stratum corneum, 
but small enough to enter into the opening of hair ducts. As the diameter 
of hair ducts in humans is generally in the range from about 70 .mu.m to 
about 1 micron in size, the particles are generally in the range from 
about 0.01 micron to about 1 micron. 
To avoid overheating of surface skin tissue, the light source should be 
absorbed by the contaminant, but should penetrate skin with a minimum of 
absorption and scattering therein. If a laser is the light source, any of 
the lasers useful in treatments to inhibit hair growth by infiltrating a 
contaminant into hair ducts can also be used in the practice of this 
invention. In one embodiment, the contaminant contains carbon particles, 
and the light source is a Nd:YAG laser providing short pulses of light 
having the following properties: 
Wavelength about 1064 nm 
Beam Shape: circle or square 
Beam Size: about 8 mm (circular) of 7.times.7 mm (square) 
Fluence 1-2 J/cm.sup.2 
Pulse energy 0.5 J/pulse 
The clinical manifestations and course of a Herpes episode depend on the 
anatomic site of the infection, the age and immune status of the host, and 
the antigenic type of the virus, i.e., whether HSV-1 or HSV-2. The spread 
of virus to the skin from peripheral sensory nerves helps explain the 
large surface area that may be affected, and the high frequency of new 
lesions distant from the initial crop of vesicles. 
Individuals who are particularly susceptible to Herpes infections in skin 
are those who are immunocompromised and those who manifest other types of 
skin conditions indicative of immunocompromise. For example, individuals 
with psoriasis, Darier's disease, eczema herpeticum, or atopic eczema are 
thought to be susceptible to cutaneous HSV infections due to reduced 
numbers of circulating NK cells and a decrease in IL-2 receptors in the 
diseased tissue (H. M. Goodyear, Br. J Dermatol 134: 85-93, 1996). In such 
individuals, the method of this invention is particularly useful either 
prophylactically to prevent reactivation of the virus in skin lesions, or 
as a treatment of an existing viral activation or reactivation. 
The mechanisms by which various stimuli cause reactivation of HSV infection 
are not known. Ultraviolet light, immunosuppression, and trauma to the 
skin or ganglia are associated with reactivation. Some hair removal 
techniques that cause trauma to the skin, such as waxing, use of 
contaminants in hair ducts, or use of chemical depilatories, may trigger 
an outbreak of Herpes in the skin section involved. The method of this 
invention is also effective for treating skin to prevent such outbreaks or 
eradicate Herpes virus throughout hair ducts when a manifestation of a 
viral infection has been triggered by hair removal techniques that cause 
trauma to the skin, even if the hair ducts involved no longer contain 
hairs. 
By the methods of this invention, Herpes outbreaks on skin can either be 
prevented or treated without reliance upon systemic administration or 
topical application of an anti-viral agent. Thus, patients with low 
tolerance for such agents, or who choose to avoid exposure to drugs, can 
be treated using a relatively inert contaminant, e.g., carbon particles 
and light. 
No. 12: A Method for Reduction of Sweat and Body Odor 
Human bodies produce sweat to reduce overheating and in response to 
emotional stimulae. Sweat is produced by glands (sudorific or sweat 
glands) situated at a depth of about 1 to 2 mm below the surface of the 
skin on almost all of the body surface. Bacterial action causes decay of 
proteinaceous compounds in sweat, creating undesirable body odors. Prior 
art methods for reducing production of sweat and/or treating body odor 
include various creams, gels and powders that block production of sweat or 
combat growth of bacteria. 
Laser treatment can be used to reduce human odor and/or the production of 
sweat. In this invention, known laser hair removal methods are modified 
for use in inhibiting production of sweat from sweat glands. 
Sweat glands are distributed widely over the surface of the skin and are 
found in almost all locations of the body. In the present invention, a 
section of skin containing sweat glands is infiltrated with a contaminant, 
for example one containing carbon particles. The particles are infiltrated 
into spaces in or adjacent to sweat glands via hair ducts. Then the skin 
surface is illuminated with short pulses of laser light that is 
preferentially absorbed in the particles, but is minimally absorbed in 
skin. As the blood vessels that supply blood to sweat glands are located 
at a depth of about 1 to about 2 mm below the surface of the skin, during 
illumination of the skin surface with the short pulses of light, a lens 
with a short focal length is used to focus the light at a depth of about 1 
to about 2 mm below the skin surface to destroy the sweat glands. In one 
embodiment, a light with a wavelength in the range from about 532 nm to 
about 600 nm is used to destroy blood vessels supplying blood to sweat 
glands. Once the skin surface has been illuminated so as to denature the 
sweat glands and/or the blood vessels feeding the sweat glands, the 
production of sweat and/or body odor in the section of skin so treated is 
reduced or eliminated. 
Alternatively, production of sweat can be inhibited by orally administering 
sodium fluorescein to a subject, waiting for the sodium fluorescein to 
accumulate in sweat glands, and then illuminating a skin section in which 
inhibition of sweat is desired with light having a wavelength that is well 
absorbed by the contaminant sodium fluorescein, but is not well absorbed 
in skin tissue. Sodium fluorescein is a biocompatible photosensitizer, and 
when administered orally is preferentially delivered to sweat glands by 
metabolic processes within about one hour in sufficient concentration to 
serve as a light-absorbing chromophore. Metabolic processes will 
eventually deliver the photosensitizer to other skin tissue, so it is 
important to time the illumination of skin tissue for destruction of sweat 
glands during the window of time when a tissue destroying amount of the 
photosensitizer has accumulated in the sweat glands, but before a tissue 
destroying amount of the photosensitizer has accumulated generally in skin 
tissue. 
A tissue-destroying amount of a solution of disodium fluorescein generally 
contains a concentration of about 2% to about 10% by weight, with the 
total amount varying depending on such factors as the weight and 
metabolism of the subject. 
Although any light can be used that produces a wavelength of about 441 nm, 
a preferred light source is a He:Cd laser or a Nd:YAG doubled frequency 
laser. Upon activation by light at a wavelength of about 441 nm, sodium 
fluorescein emits energy in the form of a green light that is well 
absorbed by blood in capillaries that feed the sweat glands, causing the 
chromophores in the blood to become heated. By this means of energy 
transfer, the blood in the capillaries is heated sufficiently to damage 
the blood supply to the sweat glands, e.g., by coagulation of the 
capillaries. Thus, the blood supply to the sweat glands is cut off or 
diminished sufficiently to cause the sweat glands to wither, inhibiting 
production of sweat and consequent odor. 
The methods for reducing human sweat and body odor of this invention offer 
the advantage that inhibition of sweat production is long term; whereas 
prior art methods in which a cream or ointment is applied to skin inhibit 
sweat production only for a few hours, at most. 
No. 13: Tailored Laser Assisted Hair Removal 
Current methods of laser assisted hair removal utilize a set of laser 
parameters that are selected to fit the absorption characteristics of a 
particular exogenous chromophore applied to the hair ducts or a particular 
naturally occurring chromophore, such as water, blood or melanin. If the 
laser parameters are adjusted at all to fit individual patients, they are 
commonly adjusted by hand to accommodate such factors as individual 
differences in skin or hair coloring, differences in follicle depth at 
different anatomical locations, and the like. It would be advantageous to 
have a more systematic method for optimizing laser parameters to fit 
individual requirements, or an automated system whereby upon input of 
information regarding an individual's coloring, etc., the system would set 
a laser apparatus to provide optimal laser parameters corresponding to the 
input information. 
A method is provided for tailoring laser-assisted hair removal to the needs 
of an individual patient. The treatment regimen and selection of treatment 
parameters is based on consideration of answers to a set of predetermined 
questions regarding various aspects of a patient's characteristics and 
treatment history that will affect selection of laser parameters and 
scheduling of treatments. The set of questions should comprise at least 
the following: (a) what is the patient's skin coloration, e.g., whether 
dark or fair; (b) what is the anatomic site of treatment, and what is the 
average depth of hair follicles at the site; (c) what is the current 
status of the hair growth cycle for the preponderance of hairs at the 
site; (4) what is the individual hair physiology of the patient at the 
treatment site, e.g. the diameter of the hairs or whether the hairs are 
vellum; and (5) what previous laser treatment for hair removal has the 
patient undergone. 
In one embodiment of the invention, a system is provided for 
pre-programming a laser to select optimal laser parameters based on input 
to the system by an operator regarding the answers to these questions, 
which are specific to an individual patient. However, the same result can 
be accomplished by the operator manually adjusting the laser parameters 
that control the energy level produced by the laser in accordance with the 
answers to the above set of questions provided by the individual to be 
treated. 
The optimal laser characteristic in terms of wavelength, fluence, pulse 
repetition rate, and pulse duration generally will vary depending upon the 
hair coloration of the individual undergoing treatment as well as skin 
color, extent of sunburn, etc. Dark hair, for example, may be more 
susceptible to a Nd:YAG laser at a wavelength of 532 nm compared to light 
hair, which is more susceptible to a wavelength of 1064 nm. In general, 
dark hair absorbs light energy more readily at any wavelength, so less 
laser energy is needed in treatment of dark hair than in treatment of 
light colored hair. 
The optimal laser characteristics for specific anatomic sites also differ 
due to differences in the average depth of hair follicles at various 
anatomical sites. For example, the energy levels utilized in the upper lip 
region may be less due to the shorter depth of the follicles (1.8 mm) 
compared to the lower leg region where the follicles may extend to 4.0 mm 
deep. As described in detail in Section No. 1, herein, the depth of an 
individual hair follicle also varies depending upon its current phase in 
the hair growth cycle. In general, the bottom of a hair follicle is at a 
depth in the range from about 1 mm to about 2 mm during the telogen phase 
of the hair growth cycle; whereas the bottom of the hair follicle is at a 
depth of about 4 mm to about 6 mm during the anagen phase of the hair 
growth cycle. Although, in some cases it may be desirable to omit 
consideration of the hair growth cycle completely in determining the 
average depth of hairs at the anatomic site to be treated, if it is to be 
considered at all, the phase in the hair growth cycle of a preponderance 
of hairs at the anatomic site generally will be considered together with 
the location of the anatomic site in determining the average depth of hair 
follicles at the site to be lased. 
It is preferred that the hairs in the section of skin to be treated will be 
synchronized in a common phase of the hair growth cycle, for example, the 
late telogen/early anagen phase, prior to lasing for hair removal, as 
disclosed in Section No. 1 herein. Assessment of the hair growth cycle for 
an individual may include a direct measurement of the extent of anagen 
versus catagen hair. This can be done by shaving or cutting the hair from 
a specific anatomic area and counting the hairs which are present. After 
one to eight weeks, the hairs in the same area are recounted using the 
same procedure. The difference between the initial count and the second 
count gives the number of hairs which are in anagen. Further description 
of procedures for assessing the current phase of the hair growth cycle in 
a section of skin and for synchronizing hairs in the hair growth cycle is 
in Section No. 1 herein. 
The hair physiology of the patient will also influence the selection of 
laser parameters. For instance, if the patient has undergone previous 
laser treatment for hair removal, the hairs at the site to be treated may 
already have undergone a substantial weakening in their general vitality, 
which is generally characterized by a decrease in diameter and less deeply 
colored appearance. Another factor relating to hair physiology that may 
influence the selection of laser parameters or treatment regimen is the 
patient's nutritional status or disease state. For example, use of 
steroids or biotin deficiency, which cause temporary hair loss, generally 
indicate that treatments for hair removal should be delayed until normal 
health has been restored. 
The scheduling of hair removal treatments, i.e., the treatment regimen, is 
also an important aspect of tailoring the hair removal treatment to the 
individual patient. In particular, the spacing between hair removal 
treatments should be closely coordinated with the patient's individual 
response to the previous treatment. For some patients, hairs do not fall 
out at a treatment site for about 2 to 3 weeks following a laser hair 
removal treatment, while for other patients the hairs at a treatment site 
do not fall out for about 6 or 7 weeks following a laser hair removal 
treatment. Therefore, if the patient has previously undergone laser hair 
removal treatment, the treatment site should be closely monitored to 
detect the loss of hair attributable to the laser treatment. New hairs 
will emerge from the hair ducts in the treatment site within about 2 to 3 
weeks following hair loss. Therefore, a subsequent treatment should be 
scheduled to take place within about 2 to 3 weeks following hair loss due 
to a previous hair removal treatment and when less than about 30% of the 
hairs at the former treatment site are visible above the skin surface in 
regrowth. If this pattern is followed, hair regrowth will be effectively 
curtailed at the treatment site. 
The spacing of hair treatments is also affected somewhat by seasonal and 
circadian rhythms in light. For example, in the Northern hemisphere, the 
largest percent of hairs in telogen phase occurs in the months of August 
and September, with onset of an increase in the percentage of hairs in 
anagen phase occurring about three months thereafter. 
The treatment regimen and the laser parameters for use in hair removal 
treatments are selected based upon the information obtained by answering 
the full set of questions, except that any question is omitted that does 
not apply to a particular individual in the judgment of a skilled 
operator. This process ensures that all relevant factors are properly 
evaluated and weighed against one another in selecting the spacing between 
hair removal treatments and the wavelength of light, fluence, pulse 
repetition rate, and pulse duration to optimize any type of laser hair 
removal technique. 
In one embodiment, the laser energy, i.e., combination of the wavelength, 
fluence, pulse repetition rate, and pulse duration of the laser, is 
selected to deliver a fluence of about 1.5 to about 5 J/cm.sup.2, for 
example about 2.5 J/cm.sup.2, at a depth corresponding to the depth of the 
majority of the hair follicles in the skin section to be treated, with the 
wavelength being selected based upon the individual's hair and/or skin 
color, as described above. 
As discussed above, the depth to which the energy must penetrate to damage 
hair follicles will differ depending upon the predominant phase of the 
hair growth cycle. In addition, hair follicles in the anagen phase are 
more susceptible to damage by lasing than at any other phase of the hair 
growth cycle. Therefore, the optimal laser parameters utilized in treating 
a site predominantly in anagen phase will include a lower laser energy 
than is required for a site predominantly in telogen phase. 
For example, treatment of each patient may be tailored by performing the 
following series of steps with regard to an individual patient. For some 
patients it will be apparent that not all of the steps will be 
appropriate, in which case an inappropriate step is omitted, and the 
operator passes to the next step in the series. However, it is important 
for the operator to at least consider whether each step is appropriate for 
each individual to be treated. 
In one embodiment the series of questions to be considered in determining 
the optimal laser parameters comprises the following: 
Does the patient exhibit any symptoms, such as a skin rash or bad sunburn, 
that are contraindications for laser hair removal? If yes, terminate the 
treatment and reschedule at a later date. Contraindications include, but 
are not limited to, existing pregnancy; a history of metastatic skin 
tumors, such as basal cell, squamous cell, or melanoma; an HIV positive 
condition; or a mole containing a hair growing in the treatment area. 
Has the patient undergone a previous treatment for hair removal? If yes, 
schedule the next treatment to occur when hair regrowth is visible from 
about 30% of the hair ducts at the previously lased site. 
What is the color of the patient's hair and skin at the anatomic site to be 
treated? Where is the anatomic site to be treated? Preferably the anatomic 
site to be treated will be photographed to document hair and skin 
coloration. Select a wavelength of light to be used based on skin color 
and hair color. 
Optional: What is the predominant phase in the hair growth cycle of hairs 
in the site to be treated? It may be desirable to avoid this question to 
save the costs involved with obtaining an answer to this question. 
The site may optionally be pretreated to synchronize the growth of hairs in 
the hair growth cycle to fix the average depth of the hair ducts (or 
follicle) at a common depth at the anatomical site. Preferably the hairs 
are synchronized in the late telogen/early anagen phase. 
Select optimum laser operating characteristics, such as wavelength, fluence 
and pulse duration based on the foregoing information. The correlation 
between patient characteristics and laser parameters is empirically 
determined. 
Initiate laser injury of the follicles to induce hair growth inhibition. 
One of skill in the art will be able to determine whether additional 
questions need to be answered in arriving at a set of laser parameters 
that are tailored to an individual patient. 
This invention provides the advantage that the laser parameters used in 
treatments to inhibit hair growth and the treatment regimen are tailored 
to fit individual characteristics of the patient, rather than using a 
fixed set of parameters for all individuals that is selected to fit the 
absorption characteristics of a particular exogenous or endogenous 
chromophore to be irradiated. In addition, as shown in FIG. 24, the method 
can be used in connection with a computerized system 72 in communication 
with a laser 74 so that the laser operator can key in responses to a set 
of predetermined questions regarding the patient's hair, skin, physical 
condition, and anatomical location to be lased with the result that a 
preprogramed selection of individually tailored laser parameters is 
transmitted to the laser before lasing is initiated. 
No. 14: Improved Laser Operating Characteristics for Hair Follicle Damage 
A number of methods are known for using lasers to inhibit hair growth 
and/or cause damage to hair follicles in a section of skin, including a 
method for infiltrating into hair ducts a contaminant containing carbon 
particles suspended in an oil, and irradiating the section of skin with 
pulses of laser light. 
The optimal laser operating characteristics have now been discovered for 
inducing targeted hair follicle damage when a contaminant containing 
carbon particles suspended in a liquid, such as an oil, is infiltrated 
into hair ducts, and the section of skin containing the hair ducts is 
irradiated with pulses of laser light. These improved parameters are as 
follows: 
Laser Type: Nd:YAG 
Wavelength 1064 nm 
Beam Shape: Circle or Square 
Beam Size: .ltoreq.8.0 mm 
Fluence: &gt;2 J/cm.sup.2 
Pulse Duration: Depends upon many factors, including: 
1. The size of carbon particles or other chromophores in the contaminant. 
2. The concentration of the chromophore in the lotion or solution applied 
to the skin prior to lasing. 
3. The depth of hair follicle (which is dependent on the anatomical site 
and the phase in the hair growth cycle). 
4. The thermal properties of the chromophore. 
The effect of pulse duration on heating and/or explosion of chromophore 
particles is described in full detail in Section 4 herein. 
For a 10 ns pulse of about 2 to about 3 J/cm.sup.2 fluence, a carbon 
particle size much less than 1 micron is needed for the photothermal 
effect to be greater than the photomechanical effect. Longer pulse 
durations are preferred with larger particles. However, when larger 
particles are used, surface cooling of the skin, for example, as disclosed 
herein in Sections 3 and 20, may be needed to avoid over heating and 
damage to surrounding skin. 
No. 16: In Situ Formation of a Photoreceptor for Use in Laser Hair Removal 
or Skin Rejuvenation Treatments 
Widespread use of lasers to remove tattoos has demonstrated that residual 
carbon in skin structures is not permanent. However, the mechanism used by 
the human body to clear residual carbon particles introduced into hair 
follicles and other skin structures during treatments for laser hair 
removal or skin rejuvenation is an open question. Additional exogenous 
chromophores useful in performing laser hair removal or skin rejuvenation 
treatments would be desirable. 
It is known that elemental iron is readily taken up by the body and used to 
replenish the approximately 1 mg of the element that is lost daily from 
shedding of senescent cells along the gastrointestinal and genitourinary 
tracts, and from desquamation of skin. This minimum daily requirement is 
increased by growth spurts, pregnancy, and pathologic hemorrhage 
(Harrison's Principles of Internal Medicine, 13th Edition, Ed. Isselbacher 
et al., Vol. 2, 1994, page 1722). Because of these factors, iron oxide has 
been safely applied to human skin and hair in cosmetics for centuries. 
Iron oxide is also an especially safe exogenous chromophore for use in any 
of the hair removal or skin treatments wherein an exogenous chromophore 
applied to the skin is irradiated, as it is highly unlikely that harmful 
effects would result from any iron that might remain in hair ducts or 
embedded in the layers of the stratum corneum. Other benign metals that 
can be substituted for iron in the practice of this invention are those, 
such as cobalt and copper, for which the human body has a dietary 
requirement. 
Iron oxide and the oxides of other benign metals can be easily formed 
within hair ducts or within other structures of the stratum corneum that 
have an opening to the skin surface. For example, iron oxide in the from 
of limonite, the trihydrate of ferric oxide, is readily formed by applying 
to skin a solution of ferric chloride e.g., in water. Upon application to 
skin, and within such skin structures such as hair ducts and sebaceous 
glands, a double replacement reaction with natural electrolytes in or on 
skin surfaces forms ferric oxide trihydrate. 
Iron oxide absorbs one or more wavelengths of light produced by infrared 
lasers. For example, limonite broadly absorbs light having a wavelength 
from about 0.1 micron to several microns, as do many inorganic compounds, 
which generally lack the sharp absorption bands characteristic of organic 
molecules. Thus, such inorganic compounds are useful for visible light 
lasers as well. Limonite appears brownish orange in color in part because 
it absorbs green light. 
The technique for loading spaces in hair ducts or surface layers of the 
stratum corneum with an oxide of a benign metal formed in situ is 
illustrated with respect to iron, but one skilled in the art can readily 
adapt the procedure for in situ formation of alternative metal oxides that 
absorb light at a frequency not readily absorbed in skin, for example in 
the infrared range. First, a skin section to be treated is coated with a 
water-based lotion or suspension comprising the metal species as a 
chloride. For iron, the lotion or suspension comprises an acid iron salt 
solution, such as ferric ammonium sulfate, ferric citrate or ferric 
chloride in water, with ferric ammonium sulfate being less harsh to the 
skin than the strongly acid chloride. The water-based suspension or 
solution optionally further comprises a suitable nonionic surfactant, such 
as Tween 20.TM. (polyoxyethylene sorbitan monolaurate), or any other 
mildly detergent compound, to overcome surface tension and thereby 
facilitate transport, i.e., "wicking," of the ferric compound into hair 
ducts. Examples of suitable surfactants for use in the invention include, 
but are not limited to, polyoxyethylene sorbitan monolaurate, Tween.RTM. 
20-50, sodium laurel sulfate, and lauric acid. 
The lotion is applied to the skin surface and allowed to stand for a few 
minutes, for example about 5 to about 20 minutes. During this rest period, 
at least a portion of the ferric salt in the lotion or suspension is 
transformed to ferric oxide trihydrate within hair ducts, within sebaceous 
glands, as well as in and around loose cells on the surface of the skin. 
However, the metal salts can be irritating in high concentrations or after 
long exposures. To avoid irritation, the metal salt can be wiped from the 
surface of the skin, and, rather than waiting for the oxide to develop by 
exposure to natural electrolytes in skin, the iron oxide is formed in situ 
by application to the skin of a basic solution, such as ammonia water or 
sodium bicarbonate. 
An exogenous chromophore produced in situ will behave similarly to prior 
art exogenous chromophores in hair removal and skin rejuvenation 
techniques. For example, such a chromophore will absorb light energy in 
the form of heat, which is then released by conduction to adjacent tissue, 
whether the chromophore is on the surface of the skin or deep within hair 
ducts. Accordingly, when surface skin cells are to be removed to 
accomplish a "peel" for the purposes of skin rejuvenation, the metal 
chloride is applied to the section of skin to be treated so that it 
infiltrates the topmost few layers of skin cells in the epidermis, and is 
allowed a period of time for the light-absorbing chromophore to 
spontaneously form. Finally the section of skin is illuminated with a 
light beam that is well absorbed by the exogenous chromophore, but which 
passes through skin with minimal absorption. In this case, the section of 
skin is generally not cleaned or wiped beyond the removal of grossly 
excessive quantities of the applied material or the in situ formed 
chromophore before application of the light beam. 
However, when the in situ-formed chromophore is to be illuminated within 
skin structures, the in situ-formed chromophore is generally cleaned from 
the skin surface prior to application of the light beam. A formulation 
containing a sufficient amount of a chelating agent for ferric oxide to 
sequester the chromophore is used for this purpose. For example, a 
solution of citric acid or ethylene diamine tetraacetic acid tetrasodium 
salt will chelate iron oxide. The chelated chromophore can be cleaned from 
the skin, for example, with a clear water rinse, prior to illumination of 
the area to be treated. Upon illumination of the cleaned skin surface with 
a light beam having at least one wavelength of light well absorbed by the 
chromophore in the hair ducts, sufficient heat can be generated to cause 
long term inhibition of hair growth, using any of the known methods 
described in the Tankovich patents incorporated by reference herein. 
For use in hair removal, formation of the exogenous chromophore within hair 
ducts of a section of skin to be treated for hair removal eliminates the 
need to mechanically force the exogenous chromophore into hair ducts by 
massage, explosion of confined particles, etc. In addition, since humans 
have a known daily requirement for certain metals such as iron and zinc, 
there is minimal risk of residual chromophore causing a problem to an 
individual treated by the method of this invention. 
No. 17: Methods for Improving a Hair Removal Process 
Under magnification, an apparently smooth skin surface is revealed as an 
uneven terrain with fissures, holes, indentations or irregularities. The 
indentations may contain minute particles of lint, dead cells, etc. These 
imperfections in the skin surface result in scattering of incident light. 
In addition, due to the change in the index of refraction between air and 
skin, photons in a light beam incident on skin, such as provided by a 
laser, tend to be reflected, refracted or scattered. As a result, a large 
portion of the light energy directed to a skin surface is lost. FIG. 25A 
shows a cross-section of a skin surface 12 with incident light beam A 
partially reflected in beam B and partially refracted in beam C. 
In this invention a method is provided for reducing light loss by 
scattering and reflection at a skin surface during skin lasing techniques. 
To reduce light loss, the skin surface is covered with a liquid coating or 
device, i.e., a window, that is transparent to incident light. The 
covering presents a smooth upper surface to incident light, and is made of 
a material having a refractive index slightly greater than, or equal to, 
the index of refraction for skin. 
It has been discovered by the inventors herein that loss of light incident 
upon a skin surface, for example during skin lasing techniques, can be 
reduced by covering the skin surface with a cover having a smooth surface. 
The covering can be provided by any material, either liquid or solid, that 
can rest atop a skin surface to be illuminated, but which will present a 
smooth surface to receive an incident light beam and transmit the beam 
without substantial attenuation to the skin surface beneath the covering. 
To accomplish this without substantial loss of light energy, the covering 
is substantially transparent to incident light, and has a refractive index 
slightly greater than or about equal to the index of refraction of skin, 
which is about 1.37. In use, the covering is placed atop the skin surface 
to be illuminated so that the incident light strikes the smooth surface 
and is transmitted to the skin through the covering. 
In one embodiment shown in FIG. 25C, the covering is a contact plate 44 
having at least one smooth planar surface 46, such as a thin plate of an 
inert and substantially transparent material. In use, the contact plate 44 
rests atop a skin surface 12. Transparent plastic, glass, quartz, fused 
silica, or a polymeric material can be used to make the contact plate 44. 
Table 5 below shows the index of refraction for representative materials 
that can be used for the contact plate. 
TABLE 5 
______________________________________ 
Material Index of Refract 
______________________________________ 
Corning glass 7913 
1.45 @1.0 .mu.m 
Glass (Bk-7) 1.51 @ 1.0 .mu.m 
Quartz 1.53 @ 1.0 .mu.m 
Fused silica 1.45 @ 1.0 .mu.m 
Styrene/vinyl benzene 
1.55 approx. 
Skin 1.37 approx. 
Mineral oil 1.47 approx. 
______________________________________ 
An antireflective coating (not shown) on the side of the covering that 
faces the laser (i.e., planar surface 46) will minimize loss of light 
energy during transfer all the way through to the skin. The contact plate 
may take a variety of shapes. For example, the shape of the contact plate 
may be circular, trapezoidal, square, etc. The skin surface to be 
irradiated may be somewhat concave or convex, depending upon its 
anatomical location. Therefore, for convenience in use, the surface area 
of the contact plate that contacts a skin surface generally covers an area 
of from a few square millimeters to a few square centimeters, and it may 
be curved rather than planar to accommodate concave or convex skin 
surfaces. 
The surface of contact plate 44 that contacts a skin surface preferably is 
sufficiently smooth to permit the device to move over a skin surface 
without abrading it, even when the device is applied to the skin with 
pressure. The contact plate may further comprise handles (not shown) to be 
grasped by an operator while applying pressure when moving the device 
across the skin, or an attachment (not shown) for directly connecting the 
plate 44 to a laser apparatus. 
In another embodiment shown in FIG. 25B, the covering is a coating 42 of a 
transparent index-matched liquid having sufficient viscosity that, when 
applied to the skin surface 12, will present a smooth surface to incident 
light beam C. When light is incident upon a smooth liquid coating applied 
over the surface of the skin, reflection losses are minimized. More light 
reaches the hair follicles beneath the coating than in the absence of the 
coating because the light is directed to the follicles in the path of the 
laser without redirection at the skin boundary. If light is directed 
perpendicularly to the smooth surface of the liquid covering, the light 
beam will pass directly into the skin without being redirected by 
refraction or scattering at the boundary of the skin as shown in FIG. 25B. 
However, scattering will occur once the light enters the skin. 
Selection of the index of refraction of the liquid controls the 
transmission of light to the skin under laser treatment. For example, the 
liquid can be a transparent oil, such as mineral oil, which has an index 
of refraction of about 1.47 as compared with 1.37 for skin. The hydrating 
effect of the oil on the skin surface also improves the smoothness of the 
skin itself. In the case where the index of refraction of the oil is 
matched as closely as possible to that of skin, the liquid coating will 
form a smooth optical boundary between the incident light and the skin to 
be illuminated. Alternatively, if the index is between that of air and of 
skin, the liquid will act as an antireflective coating to minimize 
reflection of incident light. The coating of a transparent liquid may need 
to be reapplied during the illumination phase if surface heating occurs. 
In certain prior art hair removal procedures, the skin is pretreated with 
particles of an exogenous chromophore forced into hair ducts to provide a 
heat absorbing medium around the hair follicles. When the index-matched 
liquid covering is used in conjunction with this method of hair removal, 
once the chromophore particles are worked into the hair ducts, the carbon 
particles should be cleaned off the surface of the skin, e.g., with a 
surfactant. A surfactant helps to work the carbon into the hair follicles. 
Once cleaned, the area can be covered with a clear index matching coating 
of liquid and treated with the laser light. Optionally, the skin surface 
can be coated with the liquid covering of the invention and then the 
contact plate can be applied atop the smooth liquid coating, as shown in 
FIG. 25C. By this method, loss of light energy is minimized during 
transfer all the way through to the skin. This sequence of steps will aid 
in concentrating the effects of the laser light on the hair follicle, 
thereby enhancing the treatment process. 
In yet another embodiment, the contact plate is incorporated within a domed 
reflector 48 as shown in FIGS. 26 and 27. In this embodiment, transparent 
contact plate 44 is a flat plate with smooth parallel sides, a light 
receiving side 52 and a skin-contacting side 54. The skin-contacting side 
is smooth enough to move freely over a skin surface without abrading it. 
The domed reflector further comprises a thin transparent dome 56 joined to 
the transparent contact plate along the periphery of its light receiving 
side 52. The dome is a shell, and when attached to the contact plate, 
encloses or partially encloses, an interior void space. Preferably the 
contact plate is circular and the dome is hemispherical. A handpiece 58 
can be attached to the dome to facilitate handling as shown in FIG. 27. 
The rounded interior surface 60 of the dome (e.g., hemisphere) is covered 
with a coating 72 highly reflective to light at the wavelength of the 
laser. An opening is provided in the reflective coating at the apex 62 of 
the dome 56 through which incident light can pass. Alternatively, the dome 
has an aperture 64 located at its apex through which incident light 
passes, and the interior surface of the dome is coated with the reflective 
coating. If the contact plate is circular and the dome is hemespherical, 
the aperture is generally circular as well. The reflective coating can be 
made of any reflective substance, such as silver, depending on the laser 
to be used. 
In use, as shown in FIGS. 26 and 27, the domed reflector 48 is placed atop 
a skin surface 12 to be irradiated, and light is directed to the skin 
through the domed reflector. The light enters the opening in the 
reflective coating of the dome, or through the aperture 64 at the apex of 
the dome, passes through the interior void space within the dome, and 
passes through the transparent, index-matched contact plate 44 to the skin 
surface 12. Any of the incident light photons 66 reflected or refracted 
away from a skin surface contacted by the skin-contacting side of the 
contact plate will be returned to the skin by the reflective coating on 
the interior surface of the dome. If the dome is hemispherically shaped, 
light reflected from the interior reflective surface of the dome will be 
reflected back to the skin near its point of origination. Thus the amount 
of light lost is decreased, and the efficiency of any laser skin treatment 
is increased. 
The contact plate protects the reflective interior surface of the dome from 
contamination by particles of skin, etc., that would be created by action 
of the laser upon an uncovered skin surface. In addition, the contact 
plate incorporated within the domed reflector will prevent laser action 
from exploding a chromophore off the skin surface during lasing. Further, 
the contact plate assists in forcing the chromophore particles into hair 
ducts or other skin structures during lasing. 
In another embodiment, the scatter-reducing liquid coating is applied to 
the skin surface and the domed reflector is placed atop the liquid to 
direct any reflected light back to the skin (FIG. 28). As in other 
embodiments of this invention, the liquid coating is index-matched to the 
skin so as to make a smooth optical boundary between the skin and the 
skin-contacting surface of the domed reflector. Alternatively, the skin 
surface is covered by an index-matched liquid and a contact plate with an 
antireflective coating on its smooth light receiving side is placed over 
the liquid on the skin surface for lasing (FIG. 25C). 
The methods and devices of this invention provide the advantage of reducing 
loss of incident light at a skin surface, such as during the period of 
laser illumination for skin resurfacing, hair removal, or inhibition of 
hair growth. Use of a solid covering, i.e., a contact plate or a domed 
reflector, during such procedures offers further advantages. For example, 
pressure applied to the covering (i.e., in a direction parallel to the 
direction of the laser beam path) and transferred to the underlying skin 
has a number of beneficial effects which aid in hair removal. The pressure 
compresses skin in contact with the covering device, thereby effectively 
shortening the hair duct and/or the distance from the skin surface to the 
bottom of the hair follicle because the solid covering compresses the 
upper layers of the skin. Furthermore, shortening the distance the light 
must travel to reach the bottom of the hair duct decreases the attenuation 
of light traveling to the target cells. As a result, milder lasing 
conditions are required than when the covering is not used. A third effect 
of using the covering devices during hair removal is that blood flow into 
the section of skin being illuminated can be restricted by compression of 
the capillary bed if pressure applied by the overlying device is greater 
than the patient's blood pressure. The restricted blood flow results in 
more effective delivery of laser light to the follicle and surrounding 
cellular targets, since blood can absorb a small fraction of the laser 
light. In addition, compression of the skin surface by the device reduces 
scattering of light within the skin. All of these factors aid in 
accomplishing the goal of inhibition of hair growth while minimizing 
damage to the skin surface. 
No. 18: Hair Regrowth Method Using Grafting of Papilla and Bulge Area Stem 
Cells 
It is known that papilla and mid-derm bulge area stem cells play an 
important role in the hair growth cycle. Several groups of researchers 
have reported on the key role in regulation of hair growth found in bulge 
area stem cells. In electrolysis, for example, particular attention is 
directed to destruction of hair stem cells. New ways of exploiting the key 
role of bulge area stem cells in stimulating hair growth are needed to 
combat alopecia, particularly male pattern baldness. 
The present invention provides a method for utilizing an individual's 
undifferentiated papilla and/or bulge area stem cells to stimulate hair 
growth. The inventors have discovered that bulge area stem cells can be 
harvested, isolated, cloned, and successfully transplanted into an area of 
the donor's skin where increased growth of hair is desired to increase 
hair growth therein. 
In the first step of the method, a donor section of skin is identified 
having growth of the type of hair for which increased growth at the 
recipient site is sought. Since hair types differ according to their 
anatomical site, it is generally desirable to match the hair produced by 
the donor stem cells to the type of hair that is desired at the recipient 
site. For example, in treatment of male pattern baldness, tissue samples 
are harvested from an area of the scalp that still exhibits vigorous 
growth. Once the donor site is identified, it is anesthetized locally 
using any convenient means and a plurality of tissue samples are obtained 
from the donor site. The tissue samples must contain hair follicles with 
intact undifferentiated papilla and/or dermal stem cells, as well as 
immediately surrounding tissues. Any method of tissue sampling can be 
employed, for example, punch biopsy, so long as viable stem cells can be 
obtained. 
Undifferentiated stem cells are separated out from the mid derm bulge area 
of hair papilla in the tissue samples. For example, the tissue samples can 
be microsurgically dissected to locate and separate out the stem cells. 
The separated stem cells are then cloned by culturing them in an 
appropriate growth medium, such as Dulbecco's modified Eagle's medium 
(DMEM) with fetal calf serum, for a sufficient time to allow proliferation 
and differentiation of the cells. 
Generally, the cells are cloned to a cell density of about 40 cells per 
cubic centimeter. A single growth cycle will require approximately 21 to 
28 days. During culture, the medium is kept at about body temperature, or 
37.degree. C. One skilled in the art will understand that any one of a 
number of alternative growth media can be used to foster proliferation and 
differentiation of the stem cells. Once the desired cell density is 
achieved, for instance after about 2 to 3 passages, the cloned ells can be 
examined microscopically to detect the vital cells. Healthy differentiated 
stem cells are generally identified by applying a vital dye, such as 
Hoehst 33258 or Hoehst 33342 fluorescent dyes, incubating the cells for 
about 30 minutes, and then determining which of the cells fluoresce. 
A sterile suspension of the cells in a biologically acceptable carrier 
medium, such as normal saline, is then prepared for inoculation or 
transplant into one or more recipient sites of the same individual from 
which the stem cells were harvested. Suitable carrier media include 
aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of 
non-aqueous solutions are propylene glycol, polyethylene glycol, and 
injectable organic esters, such as ethyl oleate. Aqueous carriers include 
water, alcoholic-aqueous solutions, and suspensions, including saline and 
buffered media. For interdermal grafting, the suspension of differentiated 
stem cells should be at a density of about 3 to about 10 percent by 
volume. 
For grafting of the differentiated stem cells, the recipient site is 
prepared by scraping the skin surface and making superficial incisions of 
about 200 microns in depth. The solution of stem cells is delivered to the 
recipient site, generally by pipette, and the site is covered with a 
sterile bandage, such as Tegaderm.TM.. 
In an alternative embodiment, the solution delivered to the recipient site 
additionally contains polypeptides that trigger initiation of angiogenesis 
and neurogenesis, which are expressed into the media by the stem cells 
during the cell culture mitotic process. 
If desired, a portion of the cloned stem cells can be frozen and reserved 
for future inoculation into the individual undergoing hair growth 
treatment. If frozen to a temperature of about -70.degree. C., a bank of 
auto stem cells can be kept for several months, allowing for fast 
expansion in culture when required. 
The method of the invention is illustrated in the following example: 
1. Stem cells were collected by punch biopsy from 102 healthy hair root 
canal bulge areas of an individual to be treated, and the samples were 
micro-surgically dissected to separate out and collect the 
undifferentrated stem cells from the mid-derm bulge area of hair papilla. 
2. The collected stem cells were placed for cloning into Dulbecco's 
modified Eagle's medium (DMEM) with fetal calf serum as a culture medium. 
3. When cells had proliferated and differentiated (approximately 21-28 days 
per one cycle) to about 40 cells per 1 cm.sup.3, the healthiest were 
selected and separated into three groups. 
4. One group was frozen to -70.degree. C. to create a bank of auto stem 
cells for fast reproduction when required. The second group was cloned in 
order for the secondary population to reach the cumulative population 
doublings (CDP) required, usually 2 to 10 times. 
5. The third group was used for the preparation of a sterile suspension of 
stem cells in a carrier medium. The suspension was inoculated 
interdermally by pipette into recipient sites prepared on the scalp of the 
donor individual. Alternatively, the suspension was applied topically to 
the area being treated for hair regrowth, along with polypeptides 
expressed into the media by the stem cells during the cell culture mitotic 
process. 
6. The areas inoculated with hair stem cells experienced increased hair 
growth and hair regrowth after about 21 to 28 days. 
The method of hair growth via cell transplant of this invention provides 
the advantage that cloned stem cells can be expanded in culture so that 
the amount of donor material to be transplanted is not limited by the 
number of cells that can be harvested. Thus an individual with relatively 
few donor sites can provide enough stem cells to stimulate hair growth in 
a large area of skin, if so desired. In addition, the cloned cells can be 
implanted into the recipient sites without making more than superficial 
surgical incisions in the recipient sites. In contrast, many prior art 
hair grafting procedures require use of more extensive surgical techniques 
to implant the donor tissue. 
No. 19: Method for Laser Removal of Hypertrophic and Keloid Scars 
The majority of scars heal normally over time, presenting no additional 
difficulties. However, in certain instances healing proceeds abnormally, 
generating excessive or hypertrophic scar formation. Hypertrophic scars 
remain as raised, red, "angry-looking" tissue that does not fade over 
time. Keloids are scars that continue to enlarge, forming smooth, hard 
growths, often presenting a bulging, tumorous appearance. Keloids may 
develop on any part of the body, although the upper chest and back are 
especially prone to keloid formation. Keloids occur more frequently in 
heavily pigmented individuals. 
Recently, it has been reported that postoperative low megavolt electron 
beam irradiation is effective in the prevention or recurrence of 
hypertrophic scars and keloids (Radiotherapy and Oncology, 19 (1990) 
267-272). Keloid and hypertrophic scar treatment using a carbon dioxide 
laser has also recently been described (Stem and Lucente, Arch Otolaryngol 
Head Neck Surg Sep 11, 5:9:1107-11, 1989); however, a recurrence rate of 
approximately 70% following CO.sub.2 laser therapy was reported. 
Accordingly, it would be advantageous to have new and better methods of 
laser treatment for the removal of keloids or hypertrophic scars. 
The present invention provides a method for removing keloid and 
hypertrophic scars by applying a light-absorbing contaminant to scar 
tissue to be removed so as to cause the contaminant to infiltrate the 
surface layers of the scar, and then illuminating the contaminated scar 
tissue with short pulses of light well absorbed by the contaminant, but 
which pass through normal skin tissue with minimal absorption. The 
inventors herein have discovered that repeated treatment of a scar with 
laser light will cause growth of normal epithelial cells in the area where 
the scar appeared. The method used is as follows: a contaminant is applied 
to keloid or hypertrophic scar tissue, and the area is irradiated by laser 
energy for about 5 or 6 passes, or until erythema or minor inflammation is 
detected in the scarred area. Then a period of about 4 to about 6 weeks is 
allowed to pass before the treatment is repeated. A total of from about 2 
to about 8 treatments, for example about 4 to about 6 treatments, is 
generally sufficient to cause reorganization of the epithelial layer and 
removal of the scar. A new layer of skin with the appearance and 
elasticity of normal skin will form. By a mechanism yet unknown, the 
combination of the photochemical and photothermal effects caused by 
absorption of laser energy in the contaminant and/or the scar tissue and 
underlying tissue results in (1) disappearance of the scar and (2) 
formation of new spindle-type collagen fibers in the underlying dermis at 
the place where the scar had been. 
The contaminant preferably comprises a light-absorbing chromophore of the 
type known to be useful in laser hair removal procedures, such as a 
suspension of carbon particles in an oil- or water-based medium. The short 
pulses of light are provided by a light beam with a wavelength that is 
well absorbed by the contaminant, but which has minimal absorbence in 
skin. For example, a Nd:YAG laser with a wavelength of 1064 nm can be used 
in the practice of this invention. The contaminant is applied to the scar 
tissue so as to cause penetration of the contaminant around and between 
the cells in the upper layer of the scar tissue. Brisk massage or 
ultrasound can be used to force the contaminant under and between cells on 
the surface of the scar tissue. 
The laser parameters and size of the particles in the contaminant should be 
selected so as to assure that the particles in the contaminant will 
explode upon illumination with short pulses of light. Some of the 
particles on the surface of the skin will be forced into the skin as a 
result of the shockwaves resulting from the explosion of other particles. 
In addition, the pulses of light interact with the skin and the particles 
below the skin. The particles below the skin surface that explode or 
vaporize upon illumination will rip off the layers of the hypertrophic 
scar or keloid which lay above the exploding particles. The pulses are 
continued until essentially all of the chromophore particles are exploded. 
This procedure should be repeated until sufficient layers of hypertrophic 
scar or keloid have been removed to remove the appearance of the scar. 
Laser energy not absorbed in the contaminant is harmlessly dissipated in 
the skin and surrounding tissue. There is generally minimal pain or 
feeling of heat, and no significant injury to the skin tissue. It is 
preferable to provide a slight diverging beam to assure that the beam 
spreads before it hits the skin. For example, in one embodiment, the spot 
size of the light beam at the skin surface is about 0.5 cm in diameter 
and, before interacting with the skin, the beam spreads at an angle from 
the vertical of about 10 degrees. Post-operative treatment of the targeted 
area includes any commonly accepted methods known to those in the medical 
arts. 
While the invention is illustrated with reference to the combination of a 
Nd:YAG laser and a contaminant containing carbon or graphite particles, 
persons skilled in the laser-medical arts will recognize that many other 
laser-contaminant combinations can be used to practice this invention. The 
important attributes of the combinations are: 
The contaminant must absorb light energy well at the wavelength of the 
laser beam. 
The laser beam must be a pulsed beam with very short pulses (pulse 
durations of less than 1 microsecond. 
The contaminant must be capable of being infiltrated into the upper layers 
of the scar tissue. 
The contaminant must explode with sufficient energy to tear off cells of 
the scar tissue upon absorption of the laser energy. 
The treated area must have about 2 to 8 treatments spaced at intervals of 
about 4 to 6 weeks wherein during each treatment the area is irradiated by 
laser energy for about 5 or 6 passes, or until erythema or minor 
inflammation is detected in the scarred area 
Upon laser treatment as described herein, treated scars are substantially 
removed, and new spindle-type collagen fibers are formed in the underlying 
dermis of the targeted area It is also notable that turgor of the skin is 
restored at the location where the scar had been prior to the laser 
treatment. Such results suggest that laser treatment of the afflicted area 
stimulates reorganization of tissue. According to Goslen (Physiology of 
wound healing and scar formation. In: Thomas, J. R. et al., eds. Facial 
Scars--Incision, Revision, arid Camouflage. St. Louis: C V Mosby, 1989), 
wound repair progresses normally through the following five stages: a 
vascular phase, an inflammatory phase, a re-epithelialization, formulation 
of granulation tissue, and remodeling of matrix and collagen. The final 
phase of wound healing, matrix and collagen remodeling, begins as water is 
resorbed from the scar due to the replacement of hyaluronic acid by 
proteoglycans. Cross-linking of collagen fibers proceeds by lysyl oxidase. 
Type III collagen is catabolized and replaced by type I, and the collagen 
bundles are reoriented to lie parallel to the skin surface. The metabolic 
aberration which leads to keloid formation is believed to occur in this 
late phase of scarring when keloids fail to mature and become compacted. 
Apparently, by some presently unknown mechanism, the present method of 
laser treatment returns the afflicted area to a state of wound healing 
such that in the final phase of wound repair appropriate collagen 
formation occurs, substantially avoiding formation of subsequent scars. 
This invention provides a method of laser-assisted scar removal without 
surgery. Because the treatment stimulates reorganization of tissue to 
promote proper healing, the likelihood that hypertrophic or keloid scars 
will reform is substantially reduced over the prior art methods of 
removing scar tissue. Since the majority of the laser energy is absorbed 
by the contaminant, rather than skin tissue, the risk of damaging healthy 
tissue is reduced over methods which use a laser beam that is well 
absorbed in tissue. 
No. 21: Hair Removal Using Hair Blood Supply Coagulated by Photons Guided 
by a Light-Guiding Fluid in Hair Ducts 
Hemoglobin in blood is a naturally occurring chromophore useful in hair 
removal techniques. Hair follicles are fed by a network of fine 
capillaries and blood vessels concentrated at the base of the follicles. 
U.S. Pat. No. 4,388,924 issued Jun. 21, 1983 to Weissman et al. discloses 
a method of depilation comprising directing laser energy with a wavelength 
of approximately 4800 to 5200 angstroms via a laser transmitting probe 
through the skin to terminate at the base of a hair follicle so as to 
devitalize the hair by coagulating the blood vessels at the hair root. 
However, in the Weissman method the depilation is performed one hair 
follicle at a time, rather than by applying the laser to a skin section 
containing a multiplicity of hairs for simultaneous treatment. More 
efficient ways of utilizing the natural chromophore in blood for 
inhibiting hair growth are needed. 
In this invention the combination of absorption coefficient and photon 
wavelength used for laser hair removal is selected so as to accomplish 
selective photocoagulation of the blood vessels at the end of hair 
follicles that have been filled with a light guiding medium, such as 
mineral oil, to guide photons to the hair roots. In this embodiment of the 
invention, an external chromophore is not infiltrated into hair ducts to 
absorb the energy of the laser light. Instead, the naturally occurring 
chromophores in blood are the target to which a laser is tuned. A 
combination of absorption coefficient and photon wavelength is selected to 
assure absorption of sufficient energy by blood chromophores in 
capillaries at the bottom of the hair follicle to heat the blood in the 
capillaries and surrounding epithelial tissue to a temperature of about 
70.degree. C. to about 80.degree. C. for 0.1 to 1.0 second, with the 
shorter time corresponding to the higher temperature. 
The wavelength of the laser is selected to be well absorbed in blood 
chromophores, but with a minimum of absorption in skin tissues. Blood 
absorbs photons strongly at about 400 nm with an absorption coefficient of 
about 2000 cm.sup.-1, and blood vessels can be easily coagulated by 
photons having a wavelength of about 400 nm to about 1300 nm, for example 
400 nm to about 650 nm. Moreover, photons within this wavelength range 
cannot penetrate deep into the dermis. Therefore, use of laser light 
within this range of wavelengths will coagulate the blood vessels at the 
base of the hair root, but will not destroy blood vessels below the 
epidermal layer of the skin. 
However, a large proportion of light at the above wavelengths will not 
penetrate directly through skin to the capillaries at the base of hair 
roots. To overcome this problem, a portion of the light incident on the 
skin surface is delivered to hair roots via hair ducts filled with a 
light-guiding liquid. Preferably hairs are removed from hair ducts in the 
skin section to be treated before the hair ducts are filled with a light 
guiding liquid. 
The preferred light guiding liquid is relatively transparent to light and 
has an index of refraction greater than that of skin so that a photon 
entering the light guiding liquid in the hair duct is transmitted there 
through by continuous internal reflection. For example, experiments have 
been conducted using mineral oil (index of refraction of about 1.47) as a 
light guiding liquid. These studies indicate that mineral oil is 
relatively transparent to light having a wavelength in the range from 
about 400 nm to about 650 nm. In addition, because the index of refraction 
of mineral oil is substantially greater than that for skin (index of 
refraction of about 1.37), an oil-filled hair duct will conduct light 
beams down the hair duct to the papilla area by continuous internal 
reflection, operating much the same as a fiber optic. This effect is 
illustrated in FIG. 29, which shows the path of a typical photon 1 
traveling down the hair duct 31 through the light guiding fluid 68, 
similar to photons in an optical fiber, and being absorbed in blood 
vessels 70 at the bottom of the hair duct. Other photons that do not 
strike the light guiding fluid will be absorbed (photon 1) or scattered by 
epidermis 12. 
The chromophores in the blood vessels that feed hair follicles thus receive 
illumination both from photons that penetrate and are scattered by the 
dermis, and from photons traveling down through the light guiding liquid 
in the hair duct. The laser is preferably operated in the continuous wave 
(CW) mode, and the power is set such that the temperature rise of blood at 
the hair root is high enough to denature the capillaries, but below the 
threshold for vaporization of the tissue, so that the light guiding liquid 
will not be boiled or blown out of the follicles. 
The preferred steps to be followed in practicing this invention generally 
comprise the following: 
1. Hairs are optionally extracted from the follicles to be treated using 
any known method, such as tweezing, waxing, etc. 
2. A light-guiding liquid having an index of refraction higher than that of 
skin, such as mineral oil, is applied to the skin surface and worked into 
hair ducts in the region to be treated for inhibition of hair growth. If 
possible, the hair follicles should be filled throughout with the light 
guiding liquid. However, partially oil-filled follicles are also effective 
to deliver the light into hair ducts. 
3. The surface of the skin is optionally precooled prior to application of 
the laser using any of the methods disclosed herein or known in the art. 
4. A skin section containing a multiplicity of oil-filled hair ducts is 
illuminated with short pulses of laser light that is well absorbed by 
naturally occurring chromophores in blood. 
It has also been discovered that inhibition of hair growth can be performed 
without aid from an exogenous chromophore by illuminating a section of 
skin containing hair ducts with short pulses of light at low fluence 
having a wavelength of about 1064 nm, such as is provided by a Nd:YAG 
laser. Using a light-guiding liquid in the hair duct is optional in this 
embodiment of the invention. It has been discovered that the skin contains 
naturally occurring chromophores and/or skin structures other than melanin 
that absorb light from a Nd:YAG laser at a wavelength of about 1064 nm. 
A skin section containing hair ducts is illuminated with short pulses of 
low fluence light in a beam spot size of from about 7 to 10 mm in 
cross-sectional dimension from a Nd:YAG laser at about 1064 nm wavelength. 
The fluence of the light is in the range from 0.1 to about 10 J/cm.sup.2 
and pulse duration is about 900 .mu.s to about 8 ns, for example, less 
than 1 .mu.s. Tissue associated with hair growth cells is affected (e.g., 
ablated) such that hair growth is inhibited without unwanted damage to 
skin tissue. The preferred fluence range is less than about 7 J/cm.sup.2, 
for example about 1 to about 3 J/cm.sup.2. When parameters in these ranges 
are used to illuminate the surface of a section of skin containing hair 
ducts, naturally occurring chromophores in proximity to hair growth cells 
in hair ducts absorb the short pulses of light and transfer energy to the 
hair growth cells so as to inhibit hair growth. Regrowth of hairs from 
skin sections treated according to this embodiment of the invention is 
substantially impaired. 
Low fluence Nd:YAG illumination can also be used to perform laser-assisted 
skin rejuvenation without use of an exogenous chromophore. The laser 
parameters are the same as for hair removal except that the beam spot size 
is smaller to target the beam more shallowly, for example to a depth of 
about 100 to 200 microns. 
The following examples illustrate the manner in which the invention can be 
practiced. It is understood, however, that the examples are for the 
purpose of illustration, and the invention is not to be regarded as 
limited to any of the specific materials or conditions therein. 
EXAMPLE 6 
Blood coagulation is accomplished using a laser with a wavelength of 415 
nm, a pulse duration of about 1 ms, and energy density of about 0.6 
J/cm.sup.2. This laser can be a dye laser. 
EXAMPLE 7 
Blood coagulation is accomplished using a laser at about 532 nm with a 
pulse duration of about 100 .mu.s, and energy density of about 5 
J/cm.sup.2. This laser can be a KTP solid state laser with a wavelength of 
532 nm 
The calculated increase in temperature in blood in a 5 .mu.m blood vessel 
and surrounding tissue one blood vessel radius away from the wall 
corresponding to irradiation of a skin surface with a short pulse laser is 
shown in FIGS. 30A and 30B. FIG. 30A shows the calculated temperature rise 
at the center and wall of a blood vessel as well as in the surrounding 
tissue when illuminated by photons at 415 nm wavelength with 0.2 
J/cm.sup.2 fluence and pulse duration of 100 .mu.s. FIG. 30B shows the 
similar values for 0.6 J/cm.sup.2 fluence and a pulse duration of 1 ms. 
This calculated data shows the instantaneous temperature rise in blood. At 
both fluences, the increase in temperature over normal body temperature is 
of sufficient duration to cause permanent damage to epithelial cells. FIG. 
31 shows the corresponding increase in skin temperature beneath the skin 
surface when the skin surface is maintained at 0.degree. C. by cooling. 
With pulse durations longer than 100 .mu.s, the temperature rise at the 
interface of the epidermis and dermis, where skin melanosomes are located, 
is very small so there is little risk of their destruction. 
The present invention affords several advantages over prior art methods of 
laser assisted inhibition of hair growth. First, a naturally occurring 
chromophore is irradiated by the laser and used to selectively denature 
the blood vessels that feed hair follicles. In the method of this 
invention, the laser fluence needed to coagulate the blood vessels that 
feed hair ducts is very low. In addition, since blood absorbs light waves 
at a frequency that is poorly absorbed in skin, there is reduced risk of 
unwanted damage to skin tissue or pigmentation. 
No. 22: Hair Removal by Combination of Long Pulse Laser With Skin Cooling 
There can be some disadvantages of using short pulse lasers for hair 
removal. Because the energy is transmitted so quickly into light 
absorbers, the light absorbing medium can be vaporized. The heat of 
vaporization consumes a large portion of the energy, with little energy 
remaining for transfer by thermal conduction to the target tissue. Even if 
the surface of the skin is precooled, short pulse lasers can burn the 
skin. In addition, short pulses of laser light may cause pinpoint bleeding 
from the blood vessels in the upper dermis, or these blood vessels may be 
coagulated. Another danger is that short pulse lasers can vaporize the 
melanosomes at the interface of the epidermis and dermis, resulting in 
unsightly destruction of normal pigmentation of the skin. These problems 
are overcome in the present invention by using long pulse lasers in 
combination with dynamic cooling of skin. 
Selection of pulse duration for laser skin treatment is important for 
controlling the amount of unwanted damage that is suffered in order to 
attain a desired goal. Laser hair removal techniques in which an exogenous 
chromophore is infiltrated into hair follicles present unique problems in 
the selection of pulse duration because of the difficulty of driving 
exogenous chromophore particles throughout hair ducts. 
The present invention provides an improved method for inhibiting the growth 
of unwanted hair using an exogenous chromophore, such as carbon particles, 
infiltrated into hair ducts. The method combines the use of a long laser 
pulse with dynamic cooling of the skin surface. The pulse of light used to 
heat the contaminant is long enough to avoid exploding and/or vaporizing 
the particles. The laser parameters are selected to provide a long pulse 
of light at sufficient power to heat the tissue surrounding the base of 
the hair follicle so as to cause tissue damage. To avoid concurrent damage 
to other skin tissue, the surface of the skin, which is at or near body 
temperature at the beginning of the process, is precooled. Cooling is 
continued throughout the illumination of the skin with a single long pulse 
of laser light. Then the skin surface is allowed to return to normal 
temperature before the three step process of precooling, heating while 
cooling, and return to starting temperature is repeated. 
Precooling of the skin surface establishes a steep temperature gradient 
within the skin, with temperature increasing at increasing skin depth. 
Preferably the precooling flux is sufficient to equilibrate the 
temperature of the skin surface to that of the cooling flux while allowing 
the temperature at the depth of the hair root to remain at body 
temperature . For example, a 1 second exposure of the skin surface using a 
coolant at 0.degree. C. should have sufficient flux to drop the surface 
temperature to about 0.degree. C. If the same cooling flux is continued 
during the long laser pulse, the surface of the skin will remain at about 
0.degree. C., but the skin temperature with depth will increase over that 
established during the precooling step. At the depth of the hair roots, 
the temperature should increase to about 70.degree. C. to 80.degree. C. 
for about 0.1 second. At about 50 to 100 microns depth, the level at which 
the melanosomes are found, the temperature should not rise to more than 
about 50.degree. C. to avoid damage to skin pigmentation. 
A "long" laser pulse, as used herein, is defined with reference to the type 
and size of the chromophore particles illuminated and the wavelength of 
light used. Functionally, a long pulse is a pulse long enough to 
substantially avoid exploding or vaporizing chromophore particles 
infiltrated into hair ducts. The invention is illustrated with reference 
to light at a wavelength in the range of from about 600 nm to about 1100 
nm and carbon or graphite particles in the size range of about 10 nm to 
about 1 .mu.m. At this wavelength and particle size, a long pulse has a 
duration of from about 100 .mu.s to about 100 ms. Alternatively, as used 
herein a long laser pulse can be a train of shorter pulses in such rapid 
succession that the interval between the end of one pulse and the 
beginning of the next pulse is less than the average thermal relaxation 
time of the chromophore particles. Such a train of short rapid pulses 
approximates the characteristics of a single long pulse. For example, at 
the above wavelength and carbon particle size, a train of shorter pulses 
having a pulse duration of about 1 ms to about 10 ms separated by about 1 
ms can be substituted for a single pulse having a duration longer than the 
pulse width of a single pulse in the pulse train. A chopped CW laser is 
also considered a "long" pulse laser as the term is used herein. 
A "long" pulse laser is one which releases its energy over a sufficient 
period of time that a light-absorbing chromophore surrounded by skin 
tissue, for example in a hair duct, has time to transfer energy from the 
chromophore to the surrounding tissue during the pulse. Because heat flows 
out of the chromophore into surrounding tissue, explosion of the 
chromophore particle is avoided. Generally, to denature the immediately 
surrounding tissue, the transfer of heat should be sufficient to raise the 
temperature of tissue immediately surrounding the base of the hair duct to 
about 70.degree. C. to about 80.degree. C. for a period of from 0.1 to 1 
second for a radial distance of no more than about 60 microns from the 
wall of the hair duct. It should be particularly noted that as the pulse 
duration increases, the laser energy required to accomplish the requisite 
heating and the distance to which the target temperature extends is 
increased. Therefore, for carbon particles having an average diameter from 
about 10 nm to about 1 .mu.m, a fluence of about 15 J/cm.sup.2 is used 
with a pulse duration of about 100 .mu.s, while a fluence of about 30 
J/cm.sup.2 is used with a pulse duration of about 100 ms. At a fluence of 
about 30 J/cm.sup.2 and pulse duration of about 100 ms, tissue will be 
denatured for a radial distance of about 60 microns from the wall of the 
hair duct. Further increase in the distance to which tissue is denatured 
is generally not necessary or desirable for the purposes of inhibiting 
hair growth. 
Due to the steep temperature gradient established by precooling the skin 
surface and the continued application of the cooling flux during a long 
pulse illumination, the temperature of the epidermis and upper dermis is 
kept cool enough during the laser pulse to avoid damage, while the 
temperature of the tissue surrounding a hair duct at the depth of the hair 
root increases sufficiently to inhibit future hair growth. Thus, selective 
damage of hair follicles can be achieved during laser hair removal without 
undesirable damage to other skin structures. 
FIG. 32 shows the calculated temperature rise in tissue surrounding a hair 
follicle that is filled with carbon/oil lotion and illuminated with a 60 
W/cm.sup.2 Nd:YAG laser (1064 nm) for 0.1 second. The hair follicle is 
considered as an infinitely long cylinder with a radius of a=25 .mu.m. It 
is assumed in the calculation that the follicle is filled with enough 
carbon particles so that essentially all photons striking the follicle are 
absorbed. As seen from FIG. 32, the temperature of the tissue between the 
wall of the follicle and one radius away from the wall is over 70.degree. 
C. for a period of about 0.1 second, which is enough to thermally kill the 
cells in the tissue. The goal of long term inhibition of hair growth is 
achieved when tissue up to one radius length away from the wall of the 
hair duct is thermally damaged. 
Because of absorption and scattering of photons by tissue, the photon flux 
distribution in skin decays approximately exponentially with depth. The 
light intensity at 3 mm depth may be only 25% of the incident flux. It has 
been discovered that the power density of incident light should be 240 
W/cm.sup.2 in order to have 60 W/cm.sup.2 at 3 mm depth, the average depth 
of hair follicles in an average section skin. However, a skin surface 
illuminated with 240 W/cm.sup.2 fluence of 1064 nm wavelength laser for 
0.1 second will be burned unless cooled. To succeed in providing 
sufficient power to the chromophores at the base of the hair follicle 
without burning skin tissue, other than that immediately surrounding a 
hair duct, dynamic cooling is applied to the surface of the skin section 
that is being illuminated. For example, in one embodiment the contaminant 
contains carbon particles in a size range from about 10 nm to about 1 
.mu.m, the laser wavelength is in the range of 600 nm-1100 nm, the pulse 
duration varies from 100 .mu.s to 100 ms, and the laser energy range is 
from 3 J/cm.sup.2 to 30 J/cm.sup.2 depending on the pulse duration. The 
longer the pulse duration, the higher the laser energy required. A pulse 
duration of about 100 ms is preferred. 
The area of skin surface that needs to be cooled is the area that is being 
illuminated. Therefore, the cooling medium can be applied directly onto 
the skin surface where the treatment for hair removal is sought. For 
example, the cooling effect can be accomplished by applying to the skin 
surface a continuous spray of ice water or other coolant that will be 
capable of bringing the surface of the skin to a temperature in the range 
from about 0.degree. C. to about 10.degree. C. when the cooling medium is 
applied for from about 1 to about 5 seconds. FIG. 33 above shows skin 
temperature at three different depths from the surface when the skin 
surface is cooled to 0.degree. C. for 2 seconds. After exposure of the 
skin surface to 0.degree. C. for 2 seconds, temperature in the epidermis 
and upper dermis is lowered significantly from body temperature, but the 
lower dermis remains at a temperature almost equivalent to body 
temperature, as shown in FIG. 34. 
An environmentally compatible Freon.TM. substitute, such as 
tetrafluroethene, is also suitable for this purpose. Alternatively, a 
cooling device designed to cool the surface of the skin during lasing can 
be used to administer a comparable cooling flux to the section of skin 
during lasing. Such a device is disclosed in co-pending U.S. application 
Ser. No. 60/067,460, filed on even date with this application, which is 
incorporated herein by reference in its entirety. 
Further methods of skin cooling are disclosed in Section No. 2 above. 
In summary, the method of the invention is a three step process as follows: 
1. A cooling flux is applied to section of skin sufficient to precool its 
surface to about 10.degree. C. to -10.degree. C. prior to illumination. 
Generally, the precooling period is from 1 to 5 seconds, for example one 
second. 
2. A cooling flux is maintained on the surface of the skin section 
throughout a single laser pulse. Generally the cooling flux used during 
the precooling step is continued during a single long pulse of the laser. 
The duration and energy of the long pulse is sufficient that energy 
absorbed by the contaminant and transferred to tissue immediately 
surrounding the base of a hair follicle in the section of skin destroys 
hair growth cells therein despite the temperature gradient in the skin 
established by the precooling and cooling maintained during the laser 
pulse. Generally, tissue within about 1 to 2 follicle widths from the wall 
of the hair duct (or about 30 to about 60 microns) is heated to a 
temperature from about 70.degree. C. to 80.degree. C. for a period of 
about 0.1 second by heat transferred from the contaminant during a single 
laser pulse, which is about 0.1 second in duration. The cooling flux on 
the skin surface is maintained throughout the laser pulse to protect 
tissue further than about 1 to 2 follicle radii from the wall of the hair 
follicle from damage. 
3. At the conclusion of the pulse, the cooling flux is terminated and the 
surface of the section of skin is allowed a rest period to return to body 
temperature before the three-step process is repeated. 
A total of 1 to 3 treatments is generally sufficient to cause long term 
inhibition of hair growth in a section of skin treated using the above 
method. Rather than ceasing the laser treatment during the rest period, it 
is generally convenient to use the three-step cycle in treatment of a 
different section of skin during the rest period, so long as the new 
section of skin is about body temperature at the start of the three-step 
process. If the circumference of the cooling zone is substantially the 
same size as the spot size of the laser beam, an adjacent skin section may 
be at body temperature within less than a second following the conclusion 
of the laser pulse. In any event, it may be convenient to program a laser 
to move automatically from skin section to skin section in a predetermined 
pattern so that an area of skin containing several skin sections (each one 
of which may be no larger in area than the beam spot size) is scanned in 
an orderly pattern, moving through the pattern from one to about three 
times as needed to accomplish the goal of inhibiting hair growth without 
undesirable damage to skin tissue. 
The present invention advantageously avoids production of kinetic energy 
generated by exploding or volatilizing exogenous chromophore particles in 
a hair duct, which can damage the natural chromophores at the meeting 
point of the epidermal and dermal layers, thereby disrupting the 
pigmentation of the skin surface. In addition, pinpoint bleeding in the 
skin is avoided. The present invention provides the advantage that these 
risks are completely avoided by utilizing a long laser pulse in 
combination with dynamic skin cooling. 
This aspect of the invention having been fully described, it is further 
illustrated by the examples below. 
EXAMPLE 8 
Sample calculations were performed utilizing a precooling flux applied to 
the surface of the skin section sufficient to attain a temperature of 
about 20.degree. C. at a depth of about 500 .mu.m below the surface of the 
section of skin within two seconds. If this cooling flux was maintained 
during a long pulse of laser light (60 W/cm.sup.2, Nd:YAG laser at 
wavelength of 1064 nm, pulse duration of 0.1 second), the temperature of 
the tissue surrounding the contaminant filled hair duct increased to a 
temperature of about 70.degree. C. to about 80.degree. C. for a period of 
about 0.1 second. This temperature increase is sufficient to destroy the 
cells, but higher fluence is need for damage to follicular tissue at a 
depth of 3 to 4 mm, as discussed above. 
EXAMPLE 9 
For comparison, similar calculations were made using the same laser cooling 
regimen and parameters (60 W/cm.sup.2, Nd:YAG laser at wavelength of 1064 
nm, pulse duration of 0.1 second) to determine the temperature rise of 
blood vessels in the upper dermis and in melanosomes at the interface of 
the epidermis and dermis. These calculations showed that the temperature 
rise of blood vessels with a diameter smaller that 50 .mu.m is less than 
20.degree. C. under the above laser conditions. Further calculations 
showed that under the same conditions the heat generated in an individual 
melanosome of 1 .mu.m diameter located at the interface of the dermis and 
epidermis by a laser pulse with a duration of 0.1 second is dissipated 
into the surrounding tissue without substantial increase of temperature 
over that of the surrounding skin tissue. Hence with continuous cooling of 
the skin surface during each laser pulse, as described above, the tissue 
in and surrounding a contaminant-filled hair duct can be selectively 
coagulated without unwanted burning of skin, or damage to blood vessels 
and skin pigmentation. 
No. 21: Use of Radio Waves to Control Hair Growth 
It is known to use various wavelengths of light in skin treatments and to 
cause inhibition of hair growth. Use of other types of electromagnetic 
radiation would enhance the choices, allowing the practitioner to select 
the type of radiation best suited to a particular task. 
This aspect of the invention provides a system for encouraging or retarding 
hair growth. Referring now to FIG. 36, a section of skin 100 includes one 
or more hairs 102 growing from follicles 104 in hair ducts 106. Metallic 
particles 108, for example, nanophase iron particles, are applied to the 
skin surface 110. Particles 108 may be applied as a powder, in a solution 
or in a lotion formulated for topical application. 
Referring now to FIG. 37, particles 108 are urged to enter hair ducts 106 
and move down to follicles 104. In the illustrated embodiment, particles 
108 are iron particles, which are ferromagnetic. A magnet 112 is used to 
apply magnetic repulsion to encourage at least some of particles 108 to 
enter hair ducts 106 and move down towards follicles 104. Alternatively, 
skin section 100 can be gently massaged to encourage particles 108 to move 
toward follicles 104 at the bottoms of hair ducts 106. After particles 108 
have been worked into hair ducts 106, skin section 100 can be wiped and 
gently washed clean to remove excess particles from surface 110. 
Referring to FIG. 38, a system for heating particles 108 in ducts 106 
includes a radio frequency (RF) antenna array 114, an associated power 
supply 116, and a scanning mechanism 118 for scanning RF emissions from 
antenna over skin section 100. Scanning mechanism 118 can be a mechanical 
system that moves antenna array 114, or an electronic system that 
oscillates power applied from supply 116 to antenna array 114. 
The RF radiation from antenna array 114 is absorbed by particles 108, which 
heats them. Particles 108 conduct heat to surrounding tissue in follicle 
104. The radiation can be tuned and scanned across skin section 100 in a 
manner that converges the radiation at a carefully selected depth in skin 
section 100, generally from 1 mm to about 4 mm below the surface of the 
skin. This enables the system to target damage to follicular cells in 
predetermined regions 120 of follicles 104. Depending on the phase of 
growth, thermal damage to follicle cells may activate or retard hair 
growth. 
Any metallic material or organometallic compound that absorbs RF radiation 
can be used in practice of the invention, including those in solution or 
as a free compound. Although RF radiation is well suited for heating 
nanophase iron particles, other types of radiation, such as microwave, and 
other frequencies that are matched to a particular metallic material or 
organometallic compound may also be employed. Particle sizes are not 
restricted to nanometer sizes. Particle sizes can include all sizes that 
can infiltrate the follicle and that, when combined with a suitable 
electromagnetic radiation, can provide focused heat in hair follicles 104. 
A number of embodiments of the present invention have been described. 
Nevertheless, it will be understood that various modifications may be made 
without departing from the spirit and scope of the invention. Accordingly, 
other embodiments are within the scope of the following claims.