Occupational exposures to environmental toxicants have been associated with the onset of skin lesions-including cancers. Identification and reduction of exposure to such compounds is an important public health goal. We examined the effect of cashew shell oil (CSO), used in skin tattooing for its potential to induce skin transformation in rats. Corn oil and CSO (25, 50, and 100%) were topically applied to depilated sections of Wistar' rat skin (groups: I-IV) for six weeks. Effect of treatments on serum transaminases activity, histological changes in hepatocytes and induction of micronuclei in the bone marrow were examined. In addition, CSO-induced hepatocyte proliferation was also quantified. All animals survived the course of the study. Reduced percentage change in body weight and physical trauma were observed in CSO-treated rat. The effects were more prominent in Group IV (100% CSO). Relative liver weights and number of hepatocytes (cells/mm(2)) increased significantly in groups II-IV relative to control (p < 0.05). Serum transaminases activities were not significantly (p > 0.05) affected in treated groups. Hepatic histopathology revealed moderate sinusoidal congestion (group II), in addition to portal congestion in (group III), with mononuclear cellular infiltration (group IV) animals. In addition, CSO induced significant micronuclei formation of polychromatic erythrocyte (mPCEs) in the rat bone marrow (p < 0.05) when compared with control. Topical application of CSO disrupted skin cells integrity resulting in physical trauma. In addition, CSO appears to be clastogenic and induces hepatocyte proliferation. Occupational exposure to CSO especially for engraving tattoos in humans should be discouraged and further studies need to be conducted.