Allergic Contact Dermatitis from Hair Dye

For 5 years, a 54-year-old woman had been bothered by an intermittent dermatitis on her left hand and wrist (A). The rash had remained constant during the past year. The patient, a hairdresser, usually wears gloves when she works. Moderate erythema and flaking were noted on her hands. Based on the clinical findings and the patient’s occupation, allergic contact dermatitis was strongly suspected. A thin layer rapid use epicutaneous (TRUE) test of 24 allergens revealed a significant positive reaction to p-phenylenediamine, a constituent of the permanent hair coloring preparation the patient uses in her salon (B); this substance is also found in dark-colored cosmetics, black rubber, ink, oil, grease, and gasoline. Dr Jonathan S. Crane, John D. Schoonmaker, PA-C, and Patricia B. Hood, PA-C, of Wilmington, NC, write that allergic contact dermatitis occurs after exposure-frequently multiple exposures-to an antigenic substance. This delayed hypersensitivity reaction most commonly occurs on the hands and face. Many persons are exposed to potential sensitizing agents in the workplace. A patient’s occupation often is a clue to possible allergens; as in this case, patch testing can identify the allergen and confirm the diagnosis. This patient’s dermatitis resolved after she applied a medium-potency topical corticosteroid for 2 weeks. She was advised to use a p-phenylenediamine–free hair dye on her clients and to avoid sunscreens with para-aminobenzoic acid (PABA) and preparations that contain benzocaine; these agents can cause cross-reactions in some persons with p-phenylenediamine allergy.