Peppermint Oil

Peppermint oil is the volatile essential oil obtained from peppermint, Mentha x piperita, a naturally occurring hybrid of watermint and spearmint ^[1]. It is typically produced by steam distillation of the leaves and flowering tops, and its characteristic aroma and cooling effect come mainly from menthol, accompanied by related compounds such as menthone, menthyl acetate, cineole, and limonene ^[1].

In everyday use the oil is a flavoring for confectionery, baked goods, and beverages, a fragrance in cosmetics and household products, and an ingredient in aromatherapy and topical preparations; it is also used as a natural repellent for insects and rodents ^[1]. Its best-established medicinal application, however, is in the digestive tract, where it acts as an antispasmodic ^[1].

The use of peppermint oil in irritable bowel syndrome (IBS) has been examined in numerous randomized trials and pooled analyses. Meta-analyses have found it to be more effective than placebo for both overall IBS symptoms and abdominal pain, with a number needed to treat of roughly three to four patients ^[2][4]. A network meta-analysis that compared the traditional first-line and second-line treatments for IBS ranked peppermint oil highest for improvement of global symptoms ^[3]. A 2022 update confirmed that peppermint oil was superior to placebo but cautioned that adverse events were more frequent and that the overall quality of the evidence was very low, so larger and more rigorous trials are still needed ^[1]. For this purpose the oil is usually given in enteric-coated capsules designed to survive the stomach and release their contents further down the gut ^[2].

Other reported uses include topical menthol preparations and inhaled peppermint for nausea, though the supporting evidence is weaker ^[1]. In most countries peppermint oil is sold as a dietary supplement, herbal remedy, or over-the-counter product rather than a licensed pharmaceutical, and as a flavoring it is widely regarded as safe; nevertheless it can cause side effects and is not appropriate for every situation ^[1].

Enteric-coated peppermint oil is well tolerated; the main side effects are heartburn (worse with non-coated forms), a cooling anal sensation, and occasional allergic reactions. Undiluted oil can irritate skin and mucous membranes, and it should never be applied to the face of infants due to risk of breathing problems. It can worsen reflux in people with GERD.