Topical Cetirizine in Androgenetic Alopecia: A Preliminary Study

Prostaglandin D2 (PGD2) is elevated in the bald scalp of men with androgenetic alopecia (AGA) and inhibits hair growth. Cetirizine, an H1-antihistamine, reduces PGD2 production and has anti-inflammatory effects, making it a potential therapeutic candidate.

Ten men aged 18-60 years with Norwood-Hamilton grade III vertex to V AGA applied 1 mL of 1% cetirizine in propylene glycol/butylene glycol daily for 16 weeks. Exclusion criteria included recent use of minoxidil, finasteride, or other antiandrogenic therapies. Hair counts in a 1 cm² tattoo-marked vertex area and blinded photographic assessments were evaluated at baseline and week 16.

Nine participants completed the study. Mean hair count increased from 139.6 (SE 13.9) to 163.4 (SE 15.5), a statistically significant change (p = 0.009). Blinded global photographs showed a +2 improvement in 1 patient, +1 in two, and no change in six. Trichoscopic counts improved in all patients. No adverse events occurred.

Despite limitations, this report provides additional real-world data supporting cetirizine as a potential therapy in AGA. Larger randomized controlled studies with longer follow-up are needed to establish efficacy, durability, and mechanism of action.