[DNCB therapy of alopecia areata].

Long-term treatment of alopecia areata with dinitrochlorobenzene is effective. During the last two and a half years, 227 patients who suffered, in the majority of cases, from total or subtotal hair loss, were treated by this method. Unilateral application of DNCB induced unilateral regrowth of hair in 88% of these patients. Under continuous treatment of both sides of the head, this initial response was followed by complete regrowth of hair in 78%. The same result could be obtained by application of squaric acid dibutylester, another potent contact allergen. This indicates that the essential mechanism is contact allergy. Possibly, the regrowth of hair is due to the induction of local nonspecific immunosuppression.