The concept of using a laser to produce the required injury and thus prevent the growth of unwanted hair has existed since the early days of laser use in medicine. Many different wavelengths of laser light as well as modalities have been investigated, and various commercial systems have been developed. Each individual system has had some limited degree of success in treating certain patients with certain skin types. No one system has proven to be a panacea. In order to achieve clinical success, the ideal laser system will need to produce significant injury to the follicle without producing other post treatment sequelae.
Skin is an optically complex medium.
The photon transport in the skin depends on its absorption and scattering properties. Additionally, the optical proper-ties of human skin depend on person, anatomical location or even temperature. Commercial lasers differ by wavelength, pulse duration, and fluence, all of which have some effect on the eventual outcome of the treatment. As skin color darkens with increased amounts of melanin, the depth of penetration decreases due to competition between melanin in the skin and hair. The absorption coeffi-cient for melanin over the range of wavelengths drops by an order of magnitude moving from the shortest wavelength to the longest.