Sensitizing capacity of Disperse Orange 1 and its potential metabolites from azo reduction and their cross-reactivity pattern.

BACKGROUND Simultaneous contact allergies to Disperse Orange 1, 4-nitroaniline and p-aminodiphenylamine (PADPA), as well as to other disperse azo dyes and to p-phenylenediamine (PPD), have been reported. Cross-reactivity is one of the possible explanations for simultaneous reactions between PPD and disperse azo dyes. Some metabolites from the azo reduction of these disperse azo dyes could be sensitizers, as human skin bacteria produce azo reductases. OBJECTIVES To investigate the sensitizing capacity of Disperse Orange 1, PADPA and 4-nitroaniline, and the cross-reactivity between these substances and Disperse Yellow 3, its potential metabolites from azo reduction (4-aminoacetanilide and 2-amino-p-cresol), and PPD. METHOD The guinea-pig maximization test was used. RESULTS It was found that both Disperse Orange 1 and PADPA are strong sensitizers and cross-react with each other. We were unable to sensitize guinea-pigs with 4-nitroaniline tested in equimolar concentrations to Disperse Orange 1. CONCLUSIONS The results indicate that patients sensitized primarily to Disperse Orange 1 will also react to PADPA, which can be found mainly in hair dyes. PPD, 4-nitroaniline, 4-aminoacetanilide, 2-amino-p-cresol and Disperse Yellow 3 did not show any cross-reactivity with Disperse Orange 1 or PADPA.