Photothermolysis

Laser hair removal is the process of removing unwanted hair by means of exposure to pulses of laser light that destroy the hair follicle. It had been performed experimentally for about twenty years before becoming commercially available in the mid-1990s. One of the first published articles describing laser hair removal was authored by the group at Massachusetts General Hospital in 1998. Laser hair removal is widely practiced in clinics, and even in homes using devices designed and priced for consumer self-treatment. Many reviews of laser hair removal methods, safety, and efficacy have been published in the dermatology literature.

In early history hair was removed for cleanliness and fashion reasons. If the hair was cut and shaven it meant one was high class. In Ancient Egypt, hair removal was not just a fashion statement; it also served as a treatment for louse infestation, which was a prevalent issue in the region. Commonly, they would replace the removed hair with wigs, which were seen as easier to maintain and also fashionable. They would remove their hair using two methods: waxing and shaving. If they chose to wax they would use caramelized sugar, and if they wanted to shave, they would use an early form of the straight razor.

As time went on new techniques were found to remove hair such as the one found by Rox Anderson. Anderson was an MIT graduate who received his MD degree magna cum laude. He discovered that it was possible to selectively target a specific chromophore with a laser to partially damage basal stem cells inside the hair follicles. This method proved to be successful, and was first applied in 1996. In 1997 the United States Food and Drug Administration approved this tactic of hair removal. As this technology continued to be researched, laser hair removal became more effective and efficient; thus, it is now a common method in removing hair for long periods of time.

The primary principle behind laser hair removal is selective photothermolysis (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, thereby heating up the basal stem cells in the follicle which causes hair growth, the follicle, while not heating the rest of the skin. Light is absorbed by dark objects but reflected by light objects and water, so laser energy can be absorbed by dark material in the hair or skin, with much more speed and intensity than just the skin without any dark adult hair or melanin.

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