Histologic effects of ruby laser hair removal in Japanese patients

Hair removal by lasers has recently become a popular method to remove unwanted hair. However, histologic changes in human skin before and after exposure to lasers have not been thoroughly investigated. The aim of this study was to clarify the differences that occur immediately after laser exposure and 1 month after laser exposure.

Eight adult Japanese volunteers were recruited for this study. They were treated with a long pulsed ruby laser at 20 J/cm(2). A single 3-mm punch biopsy of the laser-treated sites was obtained immediately after laser irradiation and at the 1-month follow-up visit, and they were analyzed using hematoxylin and eosin, PAM, and immunohistological staining.

Immediately after laser exposure, hair follicles were very damaged and had extensive eosinophilic degeneration. One month after laser therapy, one type of hair follicle showed cystlike formations with negative proliferating cell nuclear antigen reactions (PCNA). Another type of hair follicle showed follicular mitotic figures with cytoplasmic halos. Early anagen hair follicles were apparently not treated effectively by ruby laser.

Ruby laser leads to extensive follicular damage, and hair follicles considered to be at early anagen phase were not effectively treated. This may be the reason several courses of laser therapy are required to obtain satisfactory results.