Metal working fluids (MWFs) are widely used in industry for metal cutting, drilling, shaping, lubricating, and milling. Many occupational health concerns have arisen for workers exposed to MWFs. It has been reported earlier that occupational exposure to MWFs causes allergic and irritant contact dermatitis. Previously, we have shown that dermal exposure of female and male B6C3F1 mice to 5% MWFs for 3 months resulted in accumulation of mast cells and elevation of histamine in the skin. Topical exposure to MWFs also resulted in elevated oxidative stress in the liver of both sexes and the testes in males. The goal of this study was to evaluate whether preexisting oxidative stress in the skin exacerbated mast cell influx after MWFs treatment. Oxidative stress in the skin of B6C3F1 mice was generated by dietary vitamin E deprivation. Mice were given vitamin E deficient (5-10 i.v./kg of vitamin E) or basal (50 i.v./kg of vitamin E) diets for 34 weeks. Topical treatment with MWFs (100 microl, 30%) started after 18 weeks of alimentary vitamin E deprivation. Histology of the skin after 16 weeks of exposure to MWFs revealed a 53% increase in mast cell accumulation in vitamin E deficient diets compared to mice given a vitamin E sufficient diet. Total antioxidant reserve in skin of vitamin E deprived mice treated with MWFs was decreased by 66% as compared to those mice given a vitamin E sufficient diet. GSH and protein thiols in the dermis of vitamin E deprived mice exposed to MWFs were also decreased 39 and 42%, respectively, as compared to mice given basal diet. This study clearly delineates the role of oxidative stress in enhancing mast cell accumulation caused by topical exposure to MWFs.