Brilliant Lake Red R as a cause of pigmented contact dermatitis

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Abstract
Patients (23) suffering from pigmented contact dermatitis caused by cosmetics containing Brilliant Lake Red R were observed. Commercial samples of Brilliant Lake Red R contained many ethyl acetate extractable impurities among which 1-phenylazo-2-naphthol and azobenzene were isolated and identified. To determine the responsible allergens, 5 patients were examined by patch tests with purified samples of azo-dyes and the unidentified fractions of ethyl acetate extractable impurities. Of the 5 patients tested, 3 showed weaker reactions to purified samples of Brilliant Lake Red R and 2 showed equal reactions compared to the commercial product. 1-Phenylazo-2-naphthol was a strong allergen in all cases but azobenzene was not. Some unidentified fractions also gave positive results. Patch tests were performed with 4-phenylazo-1-naphthol, 4-phenylazo-1-naphthol-2-carboxylic acid and 2,4-bis(phenylazo)-1-naphthol, as structurally related compounds derived from 1-naphthol. All gave negative results and were not detected in the ethyl acetate extractable impurities by TLC.

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