Alopecia areata is hair loss caused when the immune system attacks hair follicles, where hair growth begins. Contact immunotherapy is an experimental therapy that may be the most effective treatment for severe alopecia areata.¹ A common medication used is diphenylcyclopropenone (DPCP).

DPCP, a liquid, is "painted" on the scalp once a week. The concentration of the solution is increased at each treatment session until a mild allergic reaction occurs. Hair growth may appear within 3 months of beginning treatment.

A review of research on contact immunotherapy notes that about half of those with severe alopecia areata had a good response, but how much hair grew back varied widely.²

Side effects of contact immunotherapy include a severe rash (contact dermatitis) and swollen lymph nodes, especially in the neck.