It has been shown previously that alopecia areata can be treated with dinitrochlorobenzene (DNCB) and other contact allergens. Whether these agents work by inducing immunologic stimulation or simply a nonspecific inflammatory reaction has not been definitively demonstrated. To test the relative importance of these two mechanisms, we have randomly studied 22 patients with alopecia areata to whom either DNCB or croton oil was applied topically. Sixty-three percentage of patients without spontaneous regrowth of hair regrew hair after DNCB application. None of those treated with croton oil responded. Patients initially treated with croton oil regrew hair when treated later with DNCB. Therefore, a proved contact allergen was shown to be required for therapeutic success. Patient acceptance of the induced contact dermatitis was excellent. In light of recent data on the mutagenicity of DNCB to bacteria, other contact allergens for topical immunotherapy are being sought.
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