Occupational allergic contact dermatitis and contact urticaria caused by polyfunctional aziridine hardener

Polyfunctional aziridine (PFA) is increasingly used as a water-based cross-linker in 2-component paints, paint primers, lacquers, topcoats and other protective coatings. The cross-linker (PFA hardener) is made by reacting multifunctional acrylic monomer with a highly reactive aziridine compound. During 1992-1993, we came across 2 patients with allergic patch test reactions provoked by PFA hardener. One of the patients was a parquet layer, and the other a printer. Allergic contact dermatitis (ACD) was diagnosed by positive allergic patch test reactions to PFA hardener in a dilution series in pet.:0.3%-1% gave ++ to allergic reactions in both patients, whereas 0.1% gave a weak (+) or questionable reaction (?+), respectively. The methacrylate patch test series was negative in both patients, although gas chromatography/mass spectrometry analysis showed that PFA hardener contained 0.3% of trimethylolpropane triacrylate (TMPTA), a multifunctional acrylic monomer. One of the patients also had symptoms of contact urticaria, and a prick test with PFA hardener (1% aq.) induced a histamine-sized prick test reaction. The positive reactions with the PFA hardener and the negative reactions with the starting chemicals and additives in PFA, namely acrylates, propyleneimine and dimethylethanolamine, indicate that PFA caused ACD. This is in accordance with our previous observations, but differs from the reports of others, whose patients had been sensitized to acrylates present as remnants in the PFA hardener. As test substance, 0.5% PFA hardener in pet. is recommended for patch testing. Testing should be performed in patients with contact dermatitis if exposure to PFA has occurred. Skin prick tests may be of help to detect contact urticaria.