Hyperpigmentation and Hirsutism of Untreated Skin After Application of Bimatoprost Solution

Bimatoprost solution is cosmetically used to treat eyelash hypotrichosis. It is believed to increase lash thickness and length, but the exact mechanism of action is unknown. We report a rare case of a 64-year-old woman who noted hyperpigmentation and hirsutism of the lower eyelids and bilateral temple areas following 8 weeks of application of bimatoprost solution. She was a dermatology nurse who strictly followed the application instructions. This unique presentation suggests that direct application of bima­toprost solution to only the upper eyelid may cause extraocular and periocular hyperpigmentation as well as localized hirsutism beyond the region of application. Side effects of bimatoprost solution require further research.