Laser Hair Removal

The light is absorbed by melanin in the hair shaft and follicle. The heat damages the follicle and slows or stops hair growth. The method rests on selective photothermolysis, described by Anderson and Parrish in 1983: a brief pulse of light absorbed by a pigmented target damages that target and spares the tissue around it.

Devices used are the ruby (694 nm), alexandrite (755 nm), diode (800 to 810 nm) and Nd:YAG (1064 nm) lasers and intense pulsed light (590 to 1200 nm). Lasers produce one wavelength. Intense pulsed light produces a broad spectrum.

Only actively growing (anagen) follicles respond, so a series of sessions is needed. The AAD puts the usual series at 2 to 6 treatments, 4 to 6 weeks apart. ASPS puts it at 4 to 6 sessions. Hair that regrows is finer, lighter and fewer.

Results are best with light skin and dark hair. Epidermal melanin in darker skin competes for the light, so dark skin is treated with longer wavelengths, longer pulses and skin cooling. A 2013 review names the 1064 nm Nd:YAG as the best laser for pigmented skin.

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