Melanin absorbs some of the laser light. There is the danger of dark skin being burned in these instances so a laser beam with a lower energy level is used. For this reason also a higher level of expertise is required on the part of the clinic. Here are some estimates which can give an approximate guide. At least 2 or 3 treatments are necessary, and hair that has been waxed or removed with tweezers could need from 5 to 8 treatments.
Hair goes through cycles.
Anagen refers to the growth stage of hair. Laser treatment works best on hair that is in the anagen stage. While one laser treatment may have long lasting effects, repeated treatments are necessary for best results to catch all the hairs as they enter the anagen stage. The laser uses a wavelength of light which passes through the skin. Unlike x-rays, there is no residual left in the body.