Peppermint Oil

What it is

Peppermint oil is the essential oil of the peppermint plant. Its active principle is menthol [1]. IBS trials have used enteric-coated capsules [2], and newer capsules are designed to release the oil further down the gut [3].

How it might work

Proposed mechanism: peppermint oil may relax the smooth muscle of the gut. In healthy volunteers, a single capsule reduced pressure in the upper stomach and reduced appetite while fasting, with little effect on tolerance of a meal [4].

What the research says

A 2022 meta-analysis of 10 trials (1,030 people) found peppermint oil more likely than placebo to improve global IBS symptoms (number needed to treat 4) and abdominal pain (number needed to treat 7), with very low quality of evidence [5]. A 2019 meta-analysis of 12 trials (835 people) reported similar benefits for global symptoms and abdominal pain [6]. A 2020 network meta-analysis ranked peppermint oil first for global symptoms, but only 13 of its 51 trials were at low risk of bias [7]. A 2026 review of plant remedies also favoured peppermint oil over placebo, while noting the quality of many studies was limited [8].

The newer trials were less positive. An 8-week trial of 189 adults found no significant difference between either peppermint oil formulation and placebo on the main abdominal pain endpoint [9]. A 6-week trial found both peppermint oil and placebo improved, with no significant difference between them [10]. A trial of 228 children found treatment success of 44% on peppermint oil and 37% on placebo, not a significant difference [11].

Earlier, smaller trials were more positive. In a trial of 90 outpatients taking capsules for 8 weeks, more people became free of abdominal pain than on placebo (14 versus 6) [2]. In a 4-week trial of 72 people, a small-intestine-release capsule cut total symptom scores by 40%, against 24% on placebo [12]. A 2025 umbrella review rated peppermint oil's effect as small and of low certainty [13].

Doses used in studies

Capsules in the trials contained about 180 mg of oil [10][9]. One 6-week trial took it three times a day [10]; other trials ran 4 to 8 weeks [9][12]. In children, the 2026 trial used twice-daily dosing for ages 8 to 11 and three times daily for ages 12 to 18 [11]. These are study doses, not recommendations.

Safety and interactions

Side effects: in the 2020 trial, mild adverse events were more common in both peppermint oil groups than with placebo [9]. A 2022 meta-analysis found significantly more adverse events on peppermint oil [5], while a 2019 meta-analysis found no significant difference [6]. Reflux was among the events tracked in the 2022 analysis [5].

No data were found in the studies reviewed on upper intake limits, toxic doses, medicine interactions, or use in pregnancy and breastfeeding. People who are pregnant, take other medicines, or have reflux, liver or kidney disease should ask a doctor before using it.

Caveats and open questions

Most trials are small and short, and the 2022 meta-analysis rated the overall evidence as very low quality [5]. The 2020 network analysis found that few trials had a low risk of bias [7]. Formulation appears to matter: the small-intestine version showed secondary benefits in the 2020 trial, but the colon-release version did not reach significance on main measures [9]. Long-term effects are unknown, since most trials ran 4 to 12 weeks [7]. A 2025 umbrella review concluded that the overall evidence did not support nutritional interventions for IBS symptoms, though it listed peppermint oil among those with some effect [13].