Topical minoxidil sensitization in androgenic alopecia

In a study conducted 36 years ago, 95 patients with androgenic alopecia were treated in a double-blind placebo-controlled study with either a minoxidil-containing lotion (49 patients) or a placebo (46 patients). After 6 months, 3 patients (3%) who switched from the placebo to the minoxidil lotion developed allergic contact dermatitis within 4 weeks. Patch tests confirmed minoxidil as the sensitizing agent in 2 patients, while the third was also sensitive to propylene glycol, a component of the lotion. None of the 46 patients who were treated with minoxidil for 6 months without prior placebo exposure developed contact dermatitis. The study suggests that while minoxidil is generally well-tolerated, there is a potential for allergic contact dermatitis in a small percentage of users.