Scalp Psoriasiform Contact Dermatitis with Acute Telogen Effluvium due to Topical Minoxidil Treatment.

Topical minoxidil, the only approved treatment for female pattern hair loss (FPHL), has been associated with scalp allergic contact dermatitis (ACD). We report the case of 2 female patients who developed ACD from minoxidil solution with severe telogen effluvium and psoriasiform scalp dermatitis. Scalp dermoscopy was useful to identify the psoriasiform vascular pattern, whereas patch testing made it possible to differentiate the cause of sensitization. In one case, minoxidil was the sole cause of scalp dermatitis, while in the other patient it was only the vehicle, thus permitting the patient to continue the treatment for FPHL.