Para-phenylenediamine (PPD) is an important and common cause of allergic contact dermatitis. The mechanism of sensitization is still unknown. It is believed that PPD is a prohapten and thus the balance between activation and/or detoxification processes may influence responses to PPD. Beside auto-oxidation to Bandrowski's base, PPD is enzymatically acetylated to monoacetyl-PPD (MAPPD) and to N,N′-diacetyl-PPD (DAPPD) in skin and keratinocytes.Objective
We investigated if the 2 acetylated PPD derivatives are able to elicit allergic contact dermatitis by performing epicutaneous skin tests in subjects with dermatitis.Patients and Methods
Contact allergy to PPD and the 2 acetylated derivatives (1% in petrolatum) were detected by patch testing of 455 patients with eczema from our clinic who were tested with the baseline series.Results and Conclusions
16 subjects were found to be patch test positive to PPD (3.5%). No reactions were found for MAPPD, and just 1 PPD-positive patient was positive for DAPPD (0.2%). In agreement with our earlier published in vitro data, these in vivo patch test results indicate that acetylation of PPD can be regarded as a detoxification reaction.