The primary principle behind laser hair removal is selective photo-thermolysis (SPTL), the matching of a specific wavelength of light and pulse duration to obtain optimal effect on a targeted tissue with minimal effect on surrounding tissue. Lasers can cause localized damage by selectively heating dark target matter, melanin, in the area that causes hair growth, the follicle, while not heating the rest of the skin. Light is absorbed by dark objects, so laser energy can be absorbed by dark material in the skin, but with much more speed and intensity. This dark matter, or chromophore, can be naturally-occurring or artificially introduced.
Melanin is considered the primary chromophore for all hair removal lasers. Melanin occurs naturally in the skin and gives skin and hair their color. There are two types of Melanin in hair. Eumelanin gives hair brown or black color, while pheomelanin gives hair blonde or red color.
Hair grows in several phases (anagen, telogen, and catagen) and a laser can only affect the currently active growing hair follicle (early anagen). Hence, several sessions are needed to kill hair in all phases of growth.
Multiple treatments depending on the type of hair and skin color have been shown to provide long-term reduction of hair. Most patients need a minimum of seven treatments. Current parameters differ from device to device but manufacturers and clinicians generally recommend waiting from three to eight weeks between sessions, depending on the area being treated. The number of sessions depends on various parameters, including the area of the body being treated, skin color, the coarseness of hair, the reason for hirsutism, and gender. Coarse dark hair on light skin is the easiest to treat. Certain areas, notably men’s faces, may require considerably more treatments to achieve the desired results.
Typically, the shedding of the treated hairs takes about two to three weeks. These hairs should be allowed to fall out on their own. Pulling hairs after a session can be more painful as well as counteract the effects of the treatment.
Please ask your clinician about your specific treatment and explain your specific needs in order to get a full understanding of the procedure.