Jul 4
2009

Journal of Investigative Dermatology

Photo-epilation is a technique for long-term removal of unwanted hair by thermal destruction of the hair follicle and its reproductive system (stems cells). The heat is caused by selective absorption of electromagnetic radiation emitted by different light sources, mainly by lasers and flash lamps (high-intensity incoherent and multichromatic pulsed light) or by combinations with radio frequency. As melanin is the main chromophor existing in hair follicles, the corresponding wavelength spectrum would range from ultra violet up to infrared light. Furthermore, longer wavelengths are preferred as the chromophor lies deep in the skin and the penetration of light increases with the wavelength.chica-15_large

Thus, in the range of 600–1100 nm, melanin absorption may be used for selective photothermolysis of hair follicles.

Regardless of the type of laser used, multiple treatments (three to eight) performed every 6–8 wk are necessary to achieve satisfactory results. Average rates of long-term hair reduction are reported between 70% and 90% at a minimum of 6 mo (Dierickx, 1999). The efficiency of the different light sources is comparable, except in the Nd:YAG laser, which is less effective in light-skinned patients but is the treatment of choice, and more safe in subjects with darker skin (Fitzpatrick skin type IV–VI), especially with pseudofolliculitis barbae (Weaver and Sagaral, 2003). Patients with dark hair and light skin are ideal candidates for photo-epilation. Often, regrowing hairs are thinner and lighter in color. None of the lasers mentioned, however, are effective in light or white hair. It is generally believed that hair follicles are more responsive to treatment while they are in the growing (anagen) phase. So far, there is no most favorable treatment site known; however, the chin area shows the weakest clearance rate and the back might have a high recurrence rate in some individuals (e.g., Mediterraneans).

It is important to avoid sun tanning or the use of sun-less tanners prior to treatment.

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Photo-epilation has become a common technique for hair growth control. But despite considerable technical advances in this field, these devices still have the potential to cause injury when used improperly. It is important to follow precise treatment guidelines in order to achieve safe and optimal results. The following treatment and safety guidelines are provided to assist the practitioner in the use of these devices. A detailed version of these guidelines are published in the Journal of Medical Laser Application (Drosner et al, 2001).

**taken from http://www.nature.com/jidsp/journal/v10/n3/full/5640219a.html, accessed on 01/06/09