Is incident sensitization to p‐phenylenediamine related to particular exposure patterns? Results of a questionnaire study

Evidence regarding the risk of active sensitization (AS) to p‐phenylenediamine (PPD), patch tested 1% in petrolatum, is conflicting. The objective of this study was to evaluate the relative frequency of ‘environmental’ exposures and skin reactions to products potentially containing PPD in subgroups of patients with versus without newly diagnosed contact allergy (CA) to PPD upon retesting. Patients patch tested twice with PPD between 1996 and 2004 in the Information Network of Departments of Dermatology (IVDK) network were identified and classified into 4 groups, according to the 2 test results with PPD at D3. A self‐administered questionnaire was mailed to 171 patients (response 57%). The frequency of exposure to ‘henna tattoos’, dark hair dyes, or textiles or work as hairdresser did not differ significantly between the groups. A significantly shorter median interval between the 2 patch tests was observed in the group with newly diagnosed PPD CA compared with the other groups (293 versus >700 days). The results of the study add new, if somewhat weak, evidence to the notion that patch testing with PPD may indeed carry some risk of AS, as environmental exposures to PPD were as common in the subgroup of patients with incident CA to PPD as in the remaining patients.