Outbreak of contact dermatitis related to Acticide EP® paste in a paint manufacturing factory

An outbreak of severe itching, erythematous and edematous dermatitis over the extremities and upper back developed in 8 of 17 workers in the raw-materials department of a paint manufacturing factory. The outbreak occurred during a 2-month period when Acticide EP® paste (Thor Chemical, Cheshire, UK) was used in place of Metatin® as a microbiocide (Acima Chemical, Buchs, Switzerland). To evaluate the frequency and the etiologic agent of this outbreak, a plant walk-through, examination and review of photographs of skin lesions followed by statistical analysis for association between the development of dermatitis and exposure to Acticide paste were performed. Three guinea pigs were subjected to patch tests comparing the dermatotoxicity of Acticide EP® and Metatin®. The results showed that 8 out of 17 workers (47%) suffered from contact dermatitis during the 2-month period. Stratification by occupational exposure further confirmed the association between the development of dermatitis and exposure to the Acticide paste. The dermatotoxicity test on guinea pigs revealed the marked corrosive effect of the paste and the absence of dermatotoxicity of Metatin®. After the removal of the paste from the raw material, there were no new cases of contact dermatitis at the 6 month follow-up. We conclude that Acticide EP® paste was the responsible offending agent. Because isothiazolinone derivatives are well-known antigens and 2-n-octyl-4-isothiazolin-3-one is the active ingredient in Acticide EP® paste, 2-n-octyl-4-isothiazolin-3-one is the likely cause of the dermatitis.