Paraphenylenediamine (PPDA) is a chemical with strong sensitizing properties used for dyeing of hair and textiles. Paraphenylenediamine can cross-react, resulting in allergy to other related compounds. The prevalence of PPDA sensitization varies widely. The objectives were to assess the frequency of positive patch test reactions to PPDA and related chemicals among patients with allergic contact dermatitis (ACD) and to analyze them regarding their clinical pattern, occupation and cross-reactions.

Material and methods:
The sociodemographic and clinical data of patients with positive patch tests to PPDA, N-isopropyl-N-phenyl-4-phenylenediamine (IPPD), ethylenediamine (EDA), triethylenetetramine (TETA) and toluene-2,5-diamine (TDA) were analyzed. The frequency, strength and cross-reactions with other chemicals were assessed.

Of 4087 ACD patients patch-tested between 2006 and 2015, positive reactions to PPDA and other amines were found in 166 (4.1%). The occupational character of PPDA allergy was established in 34.3% of patients. Personal history of atopy was reported by 36.7% of pa-tients. In 98% of those examined, allergy presented as ACD, most frequently affecting hands. Hypersensitivity to PPDA was diagnosed in 77.1%, to IPPD in 20.5%, to TDA in 6%, to TETA in 1.2%, and to EDA in 0.6% of cases. The patients with an extremely strong PPDA reaction significantly more frequently showed reactions to other para group chemicals, especially to benzocaine.

Paraphenylenediamine was a major cause of contact allergy of diverse clinical picture more often affecting women, especially with atopy. Every fifth PPDA-allergic person exhibited hypersensitivity to other related compounds. Strong reactions to PPDA increased the risk of cross-reactions.