mentha piperita (peppermint) oil, mentha piperita (peppermint) leaf extract, mentha piperita (peppermint) leaf, mentha piperita (peppermint) leaf water are obtained from the mentha piperita plant. the oil is currently used in cosmetic formulations as a fragrance component, but previously had been also described as a denaturant. the extract and leaves are described as biological additives, but only the extract is reported to be used. peppermint water is described as a flavoring agent or fragrance component, but is not currently in use. peppermint oil is used at a concentration of < or = 3% in rinse-off formulations and < or = 0.2% in leave-on formulations. peppermint oil is composed primarily of menthol and menthone. other possible constituents include pulegone, menthofuran, and limone. most of the safety test data concern peppermint oil. the oil is considered to present the "worst case scenario" because of its many constituents, so data on the oil were considered relevant to the entire group of ingredients. peppermint oil was minimally toxic in acute oral studies. short-term and sub-chronic oral studies reported cystlike lesions in the cerebellum in rats that were given doses of peppermint oil containing pulegone, pulegone alone, or large amounts (>200 mg/kg/day) of menthone. pulegone is also a recognized hepatotoxin. repeated intradermal dosing with peppermint oil produced moderate and severe reactions in rabbits, although peppermint oil did not appear to be phototoxic. peppermint oil was negative in the ames test and a mouse lymphoma mutagenesis assay but gave equivocal results in a chinese hamster fibroblast cell chromosome aberration assay. in a carcinogenicity study of toothpaste and its components, no apparent differences were noted between mice treated with peppermint oil and those treated with the toothpaste base. isolated clinical cases of irritation and/or sensitization to peppermint oil and/or its constituents have been reported, but peppermint oil (8%) was not a sensitizer when tested using a maximization protocol. it was expected that dermal absorption of peppermint oil would be rapid, following that of menthol, a major component, but in no case would be greater than absorption through the gastrointestinal tract. because of the toxicity of pulegone, the safe concentration of this constituent was limited to < or = 1%. this concentration was achievable both by controlling the time of harvest and processing technique. there is evidence that menthol can enhance penetration of other agents. formulators were cautioned that this enhanced penetration can affect the use of other ingredients whose safety assessment was based on their lack of absorption. with the limitation that the concentration of pulegone in these ingredients should not exceed 1%, it was concluded that mentha piperita (peppermint) oil, mentha piperita (peppermint) extract, mentha piperita (peppermint) leaves, mentha piperita (peppermint) water are safe as used in cosmetic formulations.