title: Brilliant Lake Red R as a cause of pigmented contact dermatitis.
abstract: Twenty-three patients suffering from pigmented contact dermatitis caused by cosmetics containing Brilliant Lake Red R were observed. Commercial samples of Brilliant Lake Red R proved to contain many ethyl acetate extractable impurities; 1-phenylazo-2-naphthol and azobenzene were isolated and identified. To determine the responsible allergens, five patients were examined by patch tests with purified samples of azo-dyes and the unidentified fractions of ethyl acetate extractable impurities. Three out of five showed weaker reactions to purified samples of Brilliant Lake Red R and the other two showed equal reactions compared to the commercial product. 1-Phenylazo-2-naphthol was found to be a strong allergen in all cases but none showed a positive reaction to azobenzene. 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 and they were not detected in the ethyl acetate extractable impurities by thin-layer chromatography.
mesh_terms: D000328:Adult; D055598:Chemical Phenomena; D002621:Chemistry; D004396:Coloring Agents / Q000009:adverse effects* / Q000032:analysis; D003358:Cosmetics / Q000032:analysis; D003877:Dermatitis, Contact / Q000209:etiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010328:Patch Tests; D010859:Pigmentation Disorders / Q000139:chemically induced*
chemical_list: D004396:Coloring Agents; D003358:Cosmetics