background. Intense pulsed light (IPL) is an effective and safe hair removal method. However, it is not exempt from side effects.

objective. To evaluate clinical and hormonal characteristics of females with facial hirsutism that developed hair growth in untreated areas close to the area submitted to IPL photoepilation (“paradoxical effect”).

methods. A total of 49 females with facial hirsutism were included in a protocol of photoepilation with an IPL source. Hyperandrogenism of tumoral origin was excluded in all subjects. Serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), prolactin (PRL), testosterone (T), androstenedione (A), dehydroepiandrosterone sulfate (DHEAS), 17-OH-progesterone (OHP), and sex hormone binding globulin (SHBG) were determined prior to IPL treatment. Clinical and photographic evaluation was performed immediately before each treatment session and 2, 6, and 9 months after the last treatment session. Only cases with “paradoxical effect” were included in this study.

results. A total of five patients with “paradoxical effect” were identified. The patients' ranged in age from 13 to 44 years and all of them had skin phototype III (Fitzpatrick scale). All these subjects were diagnosed with polycystic ovarian syndrome and presented ovarian hyperandrogenism. Patients underwent six to nine IPL sessions, and “paradoxical effect” appeared at different times during the protocol, between treatment session 3 and 6 months after the conclusion of treatment.

conclusion. IPL may induce activation of dormant hair follicles in untreated areas close to hirsute-treated areas.