p-Phenylenediamine (PPD) is an important allergen; 5.0% of patients tested positive to PPD when patch-tested, according to the North American Contact Dermatitis Group. Hair dyes are the main source of exposure.To assess the significance of PPD allergy at the Ottawa Patch Test Clinic.We assessed the epidemiology of PPD allergies and determined the cross-reactivity with other para-amino compounds. Charts of patients visiting the Ottawa Patch Test Clinic between May 1997 and July 2009 were reviewed.One hundred thirty-four patients were found to have a contact allergy to PPD; 75.4% were female, 24.6% were male, 13.4% were hairdressers, 18.7% had a history of atopy, 90.3% were sensitized by hair dye, 2.2% were sensitized by henna tattoos, and 7.5% were sensitized by other sources. Positive patch-test reactions to textile dyes were seen in 24.6%, 7.5% reacted to benzocaine, 6.0% reacted to sulfa drugs, 1.5% reacted to isopropyl-para-phenylenediamine, and 1.5% reacted to para-aminobenzoic acid.PPD is an important source of allergic contact allergy. Our results show a significant relationship of PPD with other related para-amino compounds.
