Abstract
Contact allergenicity of 2-mercaptobenzimidazole (MBI, a rubber antioxidant), methyl 2-benzimidazolecarbamate (MBIC, a fungicide) and ethylene thiourea (ETU, a rubber accelerator) was examined by a modified guinea pig maximization test with the first induction at ⪈5% and the challenge at ⪈5%. Both MBI and MBIC showed no contact allergenicity even at a maximal concentration of the first induction treatment (5%) and the challenge (5%). On the other hand, ETU had contact allergenicity by the first induction at 5 and 0.5%, and the challenge at ⪈0.5 and 5%, respectively. In addition, cross sensitization among MBI, MBIC, ETU and MBI-related compounds was evaluated. Animals treated with ETU for the first induction showed no dermal response against the challenge of MBI. In animals treated with MBI or ETU for induction no dermal response was observed against MBI-related compounds such as MBIC, 2-mercaptobenzothiazole, benzimidazole, benzene, imidazole, 2-mercapto-2-thiazoline, 2-mercapto-1-methylimidazole and thiourea. Exceptionally, guinea pigs treated with MBI for the first induction at ⪈0.5% had dermal response against the challenge of ETU at ⪈0.5%.
