Antigenic competition as a therapeutic concept for alopecia areata.

Alopecia areata can be treated effectively by topical application of potent contact allergens. To explain the response, the following hypothesis is presented. Alopecia areata is considered an autoimmune disease. The characteristic peribulbar round cell infiltrates probably reflect a cell-mediated immune reaction to some hair-associated antigen. With the elicitation of contact allergy, a second antigen is introduced at the same site. The infiltrates of the allergic contact dermatitis contain suppressor T cells and suppressor macrophages which, in terms of local immunoregulation, exert a nonspecific inhibitory effect on the immune response against hair follicles. Regrowth of hair would be due to a change in the local balance between helper and suppressor cells. In conclusion, the phenomenon of antigenic competition is proposed as a therapeutic concept.