Allergic contact dermatitis from sodium pyrithione in metalworking fluid

Case Report A 31-year-old man, with a history of occupational hand dermatitis due to metalworking fluid 1 year ago, was referred because his hand dermatitis had relapsed for 2 months. He presented with itchy nummular dermatitis of the dorsum of his fingers, spreading to his neck and face, with work-related chronology. Patch testing was performed with the revised international standard series (1), our additional series, our metalworking fluid series (TrolabA, ChemotechniqueA and personal allergens), the patient’s own protective gloves and his used metalworking fluid, this last diluted 50% o.o. and as is in a semi-open test. Readings at D2 and D4 were π/ππ to iodopropynyl butyl carbamate 1% pet., and π/ππ to sodium omadine 0.5% pet. Both tests were confirmed a few days later with ππ reactions at D2. The material safety data sheet of the actual fluid indicated the presence of sodium pyrithione, at a concentration lower than 1% in the concentrate (as provided by the manufacturer for dilution before use), and we therefore considered this test relevant. The patient denied any dermatitis after using shampoos, though did not use anti-dandruff shampoos. Iodopropynyl butyl carbamate, though not contained in the current fluid, could have been of past relevance to the patient’s previous dermatitis from cutting fluids.