Patch testing with hydroxyethyl-p-phenylenediamine sulfate - cross-reactivity with p-phenylenediamine

Background. Adverse reactions to permanent hair dyes are frequent, and primarily result from sensitization to p-phenylenediamine (PPD). Objectives. To investigate the degree of cross-reactivity to a chemically similar dye, hydroxyethyl-p-phenylenediamine sulfate (HPPS), and whether this might be a dyeing alternative for patients who are sensitive to PPD. Method. HPPS was patch tested in two concentrations in a total of 216 patients suspected of having contact dermatitis caused by hair dyes and/or hair cosmetics. A regular use test with a hair dye containing HPPS was suggested to every patient who had had an adverse reaction to a PPD hair dye in the past. Results. Forty of 216 (19.9%) patients reacted to 1% PPD, whereas only 2/216 (0.9%) showed a positive reaction to 1% HPPS. Reactivity to 2% HPPS was only slightly higher (5/216, 2.3%). On the basis of the 43 PPD-positive patients, the reactivity to 2% HPPS amounted to 12%; the corresponding figure for toluene-2,5-diamine was 15% (5/33). In a use test on two PPD-positive patients with a hair dye containing HPPS, no adverse reaction was seen, even after several years of regular dyeing. Conclusions. HPPS may be an alternative hair dye for individuals not tolerating PPD-containing dyes. However, cross-reactivity with PPD and other aromatic amines may occur. HPPS is also a known sensitizer, and the risk of de novo sensitization can only be assessed by a controlled study on a large panel and under regular use conditions.