A controlled trial of contact allergen therapy of alopecia areata (AA) using squaric acid dibutyl ester (SADBE) was performed on 17 patients. The right side of the patient's scalp was treated and the left side acted as an untreated control. Minimal signs of terminal hair growth were present in only 3 patients after 8-12 weeks of therapy. A majority of patients experienced adverse effects which led to the early withdrawal of 2 patients and the premature termination of the trial. We do not recommend the use of SADBE in the treatment of AA.