Patch test results in patients with scalp dermatitis: analysis of data of the Information Network of Departments of Dermatology

Background: Contact dermatitis of the scalp may develop primarily due to exposure to cosmetic products or secondarily due to application of topical medicaments on affected skin. Objectives: To illustrate the current spectrum of allergens in scalp dermatitis. Patients/methods: Data of 1320 patients recorded by the Information Network of Departments of Dermatology (IVDK) between 1993 and 2003, who were patch tested to confirm or rule out (secondary) allergic contact dermatitis of the scalp, were analysed. Results: Sensitization to p-phenylenediamine, tolune-2,5-diamine, p-aminophenol, 3-aminophenol, p-aminoazobenzene, cocamidopropyl betaine and pyrogallol was significantly more common than in the remaining IVDK patients. In 690 patients, altogether 4070 patients' own products were patch tested. Medical products, hair tints and bleaches (HTB) and hair-cleansing products together caused nearly 2/3 of positive patch test reactions. Among these categories, HTB showed the highest percentage of positive patch test reactions; 24 of 29 HTB-positive patients had no positive reaction to any of the commercially available allergens. Conclusions: In our subgroup of patients with scalp dermatitis, constituents of hair-colouring products were the most important allergens. As some ingredients of hair dyes are not contained in patch test series, testing of patients' own products is an important part of diagnostic workup, as otherwise sensitizations may be missed.