Toxicological effects of Mentha x piperita (peppermint): a review

Peppermint (Mentha x piperita L.) is not only used as a medicinal plant with therapeutic activity but also as a tea infusion, herb, spice or as a flavoring agent in other preparations. However, its adverse side effects on health have been described. The outcome of this review revealed that peppermint and its main constituents (pulegone, menthone, menthol and menthofuran) are moderately toxic. Peppermint and its menthol isomers possess no major innate mutagenic, genotoxic or embryotoxic properties. Peppermint essential oil interacts with cytochrome P450 isoenzymes in human liver microsomes. It is contraindicated in patients with bile duct obstruction and gall bladder inflammation. In patients with gastrointestinal reflux or hiatus hernia, its use should be exercised with caution because it may exacerbate the symptoms of gastrointestinal reflux.