Is PPD a useful screening agent?
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In this study, the usefulness was assessed of para-phenylenediamine (PPD) base as a marker for contact allergy to para-compounds and disperse dyes. 59 patients with a positive reaction to PPD were patch tested with a series of para compounds and disperse dyes. This dyes series was also tested in patients with a suspect medical history of contact allergy to hair, fabric or leather dyes. In total 610 patients were tested. As 24 patients became positive over the weekend, late readings, day 6 or 7, are important. These reactions were most probably relevant in 17/24 patients. Positive reactions to PPD correlated well with reactions to para compounds like p-aminoazobenzene and p-toluenediamine sulphate but not with disperse dyes. Reactions to Disperse Blue (106, 124) and Orange (1 and 3) were seen most frequently. PPD is a good screening agent for hair dye, but not for disperse dye, sensitivity.