Subchronic toxicity study of peppermint oil in rats

Peppermint oil was given p.o. to four groups of 28 rats at dosage levels of 0, 10, 40, and 100 mgkg body wt. per day for 90 days. At the highest dose histopathological changes consisting of cyst-like spaces scatered in the white matter of cerebellum were seen. No other signs of encephalopathy were observed. Nephropathy was seen in the male rats in the highest dose group. A no-observed-adverse-effect level of 40 mgkg body wt. per day was determined.