Abstract
Alopecia areata (AA) is a T-cell-mediated autoimmune disease affecting genetically predisposed people of all ages (approximately 0.1–0.2% of the general population). It is a nonscarring alopecia that commonly affects the scalp with one or multiple patches, or the total scalp (alopecia totalis, AT), or the scalp and body hair (alopecia universalis, AU). There are no approved medical treatments, and the choice of treatment depends on the age of the patient, the extension, and the activity phase of the disease. Immunotherapy with squaric acid dibutylester (SADBE) or diphenylcyclopropenone (DPCP) is a topical treatment without serious side effects that can be prescribed also for children. The mechanism of action of this therapy is not fully understood, but studies have shown that the contact dermatitis induced by these sensitizers changes the perifollicular CD4+/CD8+ T-lymphocyte ratio, causes antigenic competition, leads to apoptosis of autoreactive T-lymphocytes, and modulates proinflammatory cytokines. Hair regrowth rates range from 6% to 85% as reported in different studies.