Pustular Allergic Contact Dermatitis from Minoxidil

This article reports a case of pustular allergic contact dermatitis caused by the topical application of minoxidil, a drug used for hair growth. The patient, a 26-year-old woman, developed vesicular and pustular lesions on her scalp, forehead, and right eyelid after using a hydroalcoholic solution of 2% minoxidil for androgenetic alopecia for a week. Biopsy showed mild spongiosis and perifollicular lymphocytes and histiocytes, with eosinophils. The inflammatory infiltrate invaded the follicular epithelium, producing areas of reticular degeneration. The patient was treated with corticosteroids and oral antihistamines, with resolution of the lesions in 5 days. Patch tests with 2% minoxidil in ethanol and the hydroalcoholic solution of minoxidil showed positive reactions, with vesicles and pustules similar to those in the clinical lesions. The article also discusses other reported cases of allergic contact dermatitis caused by minoxidil.