Diffuse face and ear hypertrichosis caused by 5% topical minoxidil in an adult woman with spontaneous resolution

Minoxidil is a vasodilator medication known for its ability to promote hair growth. Although it was first introduced as an oral drug to treat hypertension, minoxidil was observed to have the important side-effect of increasing hair growth. This led to the development of a topical formulation as a 2% concentration solution for the treatment of female androgenic alopecia (AGA) and 5% for treating male AGA, which is considered as a first line U.S. Food and Drug Administration (FDA)-approved treatment for AGA in addition to oral 5-alpha-reductase inhibitor (finasteride). The mechanism by which minoxidil promotes hair growth is not fully understood but can be related to increasing blood flow owing to its vasodilator effects. Androgenic alopecia is characterized by the gradual conversion of terminal hairs into vellus hairs. Alterations in the hair cycle include reduced duration of the anagen phase and increased duration of the telogen phase, resulting in shorter hairs and eventual balding. Side effects of topical minoxidil include irritant and allergic contact dermatitis, pruritus, and facial hypertrichosis, which are more often seen with the use of 5% solutions rather than 2%. Herein, we report a 24-year-old woman who developed severe ear and face hypertrichosis after using a topical 5% minoxidil solution. She later had spontaneous resolution of her hypertrichosis three months after stopping it.