Histologic evaluation of a millisecond Nd:YAG laser for hair removal

BACKGROUND: Hirsutism and hypertrichosis are common problems. Laser-assisted hair removal has recently become a popular method to remove unwanted hair. However, histologic changes of the hair follicle after exposure to laser continue to require further investigation. OBJECTIVE: To determine the thermal effect of a millisecond Nd:YAG hair removal laser. METHODS: Six patients with black hair were treated with 50 msec pulsed Nd:YAG laser at fluences 30, 50 or 100 J/cm(2). Histologic examinations were performed on each laser-treated site at 24-72 hours after laser exposure. RESULTS: Fluence-dependent selective thermal injury to follicles was seen. The average depth of acute laser injury at fluences 30, 50 and 100 J/cm(2) were 1.06, 0.85 and 1.11 millimeters, respectively. CONCLUSIONS: Long-pulsed millisecond Nd:YAG lasers produce selective thermal damage of hair follicles. Varied laser fluences used in this study did not statistically alter the degree of thermal injury.