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Epilation performed by laser was performed experimentally for about 20 years before it became commercially available in the mid 1990’s. Laser and light-based methods are sometimes called phototricholysis or photoepilation.
In addition to lasers, some light-based epilators use a xenon flashlamp which emits full-spectrum intense pulsed light (IPL) . Treatment with this device is sometimes popularly referred to as laser hair removal, though the device is not a laser per se.
The primary principle behind laser hair removal is selective photothermolysis. Lasers can cause localized damage by selectively heating dark target matter in the area that causes hair growth 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 target matter, or chromophore, can be naturally-occurring or artificially introduced.
Hair removal lasers selectively target one of three chromophores:
Carbon, which is introduced into the hair follicle by rubbing a carbon-based lotion into the skin following waxing (this lotion is an “exogenous chromophore”). When irradiated by an Nd:YAG laser, the carbon causes a shock wave capable of mechanically damaging nearby cells.
Hemoglobin, which occurs naturally in blood (it gives blood its red color). It preferentially absorbs wavelengths from argons, and to a lesser extent from rubies, alexandrites, and diodes. It minimally absorbs the Nd:YAG laser wavelength.
Melanin is considered the primary chromophore for most lasers currently on the U.S. market. Melanin occurs naturally in the skin (it gives skin and hair its color). There are two types of melanin in hair: eumelanin (which gives hair brown or black color) and pheomelanin (which gives hair blonde or red color).