Contact allergy to colour developing agents: analysis of test preparations, bulk chemicals and tank solutions by high-performance liquid chromatography

: Colour developing agents which are derivatives of p-phenylenediamine can cause contact allergy. This study was done to perform if the observed simultaneous test reactions between different colour developing agents could be explained by common contaminants, reaction products or impurities. High-performance liquid chromatography (HPLC) was used for the separation of p-phenylenediamine, 1,4-benzoquinone, hydroquinone, Metol and the colour developing agents CD-2, CD-3 and CD-4. The stability in water solutions and in petrolatum mixtures was examined for the last three substances. Samples of test preparations drawn at different stages of guinea pig maximization tests (GPMT) with colour developing agents were analysed, as well as patch test preparations for clinical use and tank solutions from developer machines. No contaminants or reaction products in common were shown in the bulk chemicals, tank solutions or test preparations of CD-2, CD-3 and CD-4. These findings and the GPMT studies imply that the simultaneous test reactions reflect cross-sensitization. The colour developing agents were stable in petrolatum mixtures, but unstable in water solutions. Therefore, fresh solutions for intradermal induction and petrolatum mixtures for topical induction and challenge were used in the final GPMT's.