Peppermint

What Is Peppermint?

Peppermint is a cooling, aromatic mint grown for its leaves and their essential oil. It flavours tea, confectionery, toothpaste and chewing gum, and it is one of the best-known digestive herbs in Western herbal medicine ^{34,35Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →}.

Mentha × piperita is a natural hybrid of watermint (Mentha aquatica) and spearmint (Mentha spicata), which is why its name carries the × ^{35Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →}. It rarely sets seed and spreads by underground runners ^{36Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}. It is cultivated across temperate Europe, Asia and North America, and in India and the Mediterranean ^{29Reference 29Mahendran et al. · 2020ReviewEthnomedicinal, phytochemical and pharmacological updates on peppermint (Mentha × piperita L.) — a review — reviewView study →}.

The essential oil’s main constituent is menthol, followed by menthone ^{33Reference 33European Directorate for the Quality of et al.European Pharmacopoeia — Peppermint oil (Menthae piperitae aetheroleum): gas-chromatographic composition limits}. Enteric-coated capsules of the oil have been tested in many trials for irritable bowel syndrome, and a peppermint and caraway oil combination for functional dyspepsia ^{1,2,3,4,14Reference 1Ingrosso et al. · 2022Meta-analysisSystematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome — systematic review, meta-analysisView study →Reference 2Ford et al. · 2008Meta-analysisEffect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →Reference 3Khanna et al. · 2014Meta-analysisPeppermint oil for the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →Reference 4Alammar et al. · 2019Meta-analysisThe impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data — meta-analysisView study →Reference 14Li et al. · 2019Meta-analysisA combination of peppermint oil and caraway oil for the treatment of functional dyspepsia: a systematic review and meta-analysis — systematic review, meta-analysisView study →}.

Peppermint is easily confused with spearmint, a separate species whose oil is low in menthol.

How Is Peppermint Used?

• Leaf tea — dried leaf infused in hot water, for wind, bloating and indigestion.
• Tincture and liquid extract — of the leaf, for the same digestive uses.
• Enteric-coated oil capsules — for irritable bowel syndrome. The coating releases the oil past the stomach ^{5,10Reference 5Weerts et al. · 2020RCTEfficacy and safety of peppermint oil in a randomized, double-blind trial of patients with irritable bowel syndrome — randomised controlled trialView study →Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}.
• Peppermint and caraway oil capsules — a fixed combination for functional dyspepsia ^{11,14Reference 11May et al. · 2000RCTEfficacy and tolerability of a fixed combination of peppermint oil and caraway oil in patients suffering from functional dyspepsia — randomised controlled trialView study →Reference 14Li et al. · 2019Meta-analysisA combination of peppermint oil and caraway oil for the treatment of functional dyspepsia: a systematic review and meta-analysis — systematic review, meta-analysisView study →}.
• Diluted oil on the skin — a 10% solution in ethanol, applied to the forehead and temples for tension headache ^{18Reference 18Göbel et al. · 1996RCTEffectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type — randomised controlled trialView study →}.
• Inhaled oil — for nausea ^{25Reference 25Ahn et al. · 2024Meta-analysisEffects of aromatherapy on nausea and vomiting in patients with cancer: a systematic review and meta-analysis of randomized controlled trials — systematic review, meta-analysisView study →}.

Traditional Uses

Western Herbal Medicine

There is evidence that peppermint was cultivated in ancient Egypt, and it appears in Icelandic pharmacopoeias of the thirteenth century ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}. It was described as a distinct species only in the late seventeenth century. It entered the London Pharmacopoeia in 1721 and came into general use in Western European medicine in the mid-eighteenth century, first in England ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}.

The herb and its oil were used as a stomachic and carminative, for wind, colic, abdominal cramp and nausea, and as a cordial for infants. Peppermint tea, taken with elder flower and yarrow or boneset, was a household remedy for colds and mild influenza ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}.

The oil and its menthol were used for toothache, and rubbed on the temples for neuralgic headache ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}. Peppermint has also traditionally been used for fever and for inflammation of the mouth and throat ^{29Reference 29Mahendran et al. · 2020ReviewEthnomedicinal, phytochemical and pharmacological updates on peppermint (Mentha × piperita L.) — a review — reviewView study →}.

Indications

• Irritable bowel syndrome in adults and children [enteric-coated oil] ⚠Caution: The largest trial, in 190 adults, missed its main endpoints, though abdominal pain improved. A 2022 meta-analysis found a benefit but rated the quality of the evidence as very low ^1,5.
• Functional dyspepsia [peppermint and caraway oil combination]
• Colon and duodenal spasm during endoscopy [dilute oil]
• Tension headache [10% oil on the skin]
• Nausea [inhaled oil]
• Wind, bloating and indigestion [leaf tea; Western herbal medicine]
• Colic and abdominal cramp [leaf, oil; Western herbal medicine]
• Colds and mild influenza [leaf tea, with elder and yarrow; Western herbal medicine]
• Toothache and neuralgic headache [oil, menthol; Western herbal medicine]
• Fever and sore throat [leaf; traditional use]

Botany

Peppermint is an upright perennial herb in the mint family (Lamiaceae) ^{35Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →}. Its square stems are branched, usually purplish-red, and grow 30–100 cm tall ^{35,36Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}.

The leaves grow in opposite pairs on short stalks. They are lance-shaped to narrowly oval, about 2.5–5 cm long, with unevenly toothed edges and a pointed tip. The undersides are densely dotted with oil glands ^{35,36Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}.

The small, tubular flowers are white tinged with red, or lilac-pink. They grow in whorls gathered into cylindrical spikes at the stem tips, with the lowest whorls spaced apart ^{35,36Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}. Flowering is in summer ^{35,36Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}.

Peppermint is a sterile hybrid of watermint and spearmint and rarely sets seed ^{35,36Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}. It spreads by rhizomes and is propagated by division and stem cuttings ^{36Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}.

Distribution

Peppermint originated in Europe and the Middle East ^{36Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}. It is cultivated across temperate Europe, Asia and North America, and in India and the Mediterranean ^{29Reference 29Mahendran et al. · 2020ReviewEthnomedicinal, phytochemical and pharmacological updates on peppermint (Mentha × piperita L.) — a review — reviewView study →}. In China it is grown as a crop ^{35Reference 35Li et al. · 1994Mentha × piperita Linnaeus — species description, uses and distribution — floraView study →}.

It escapes readily from gardens, and in North America it is a common garden escape ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}. It grows best in rich, moist soil ^{36Reference 36NC State Extension (n.d.)Mentha × piperita — description, origin, dimensions, leaves, flowers and cultivation — reference databaseView study →}.

Growing Conditions

Cultivation snapshot for Peppermint

SunFull sun to part shadeWaterMedium to wetSoilRich, moist soilsLifeperennialZoneUSDA 5-9

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Harvesting & Preparation

Mint is easy to cultivate indoors or out. For medicinal use and for oil, the herb is cut as the plant begins to flower ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}.

Steam-distilled leaf oil concentrates the monoterpenes and is the form used in most clinical trials. An infusion (tea) extracts mainly the water-soluble phenolics and only part of the menthol.

Peppermint oil has been adulterated with camphor, cedarwood, copaiba, rosemary and turpentine oils, and with alcohol. Menthol crystals have been cut with Epsom salts, which they resemble ^{34Reference 34Grieve · 1931A Modern Herbal — “Mints.” (historical/traditional reference)}.

Phytochemistry

The leaf’s essential oil is dominated by menthol, which makes up 30–55% of the oil under European Pharmacopoeia limits, and its ketone menthone, at 14–32% ^{33Reference 33European Directorate for the Quality of et al.European Pharmacopoeia — Peppermint oil (Menthae piperitae aetheroleum): gas-chromatographic composition limits}. Other monoterpenes include menthyl acetate, isomenthone, 1,8-cineole, menthofuran, limonene and the pinenes, over a lighter sesquiterpene fraction of caryophyllene and germacrene D ^{33Reference 33European Directorate for the Quality of et al.European Pharmacopoeia — Peppermint oil (Menthae piperitae aetheroleum): gas-chromatographic composition limits}.

Menthol is a monoterpene alcohol. It blocks calcium channels in gut smooth muscle and acts on the TRP channels that sense cold ^{10,21,22Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →Reference 21Hills et al. · 1991In vitroThe mechanism of action of peppermint oil on gastrointestinal smooth muscleView study →Reference 22Hawthorn et al. · 1988In vitroThe actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations — in vitroView study →}. Two minor monoterpenes, pulegone and menthofuran, are toxic to the liver at high doses, and the European Pharmacopoeia limits both in the oil ^{33Reference 33European Directorate for the Quality of et al.European Pharmacopoeia — Peppermint oil (Menthae piperitae aetheroleum): gas-chromatographic composition limits}.

The oil’s composition varies with the plant. One analysis of cultivated plants found menthol at about 53%, menthyl acetate at 15% and menthofuran at 11% ^{27Reference 27Saharkhiz et al. · 2012In vitroChemical composition, antifungal and antibiofilm activities of the essential oil of Mentha piperita L. — in vitroView study →}.

The water-soluble side of the leaf is different. An aqueous leaf extract contained mainly the flavanone glycoside eriocitrin (38% of the extract), with luteolin-7-O-rutinoside, hesperidin and rosmarinic acid in smaller amounts ^{23Reference 23Sroka et al. · 2005In vitroAntiradical and anti-H2O2 properties of polyphenolic compounds from an aqueous peppermint extract — in vitroView study →}. Luteolin-7-O-rutinoside is the flavonoid glycoside that inhibited histamine release in rat studies ^{32Reference 32Inoue et al. · 2002Antiallergic effect of flavonoid glycosides obtained from Mentha piperita LView study →}. Hesperidin is absorbed only after gut bacteria remove its sugar, as its aglycone hesperetin. The leaf also contains astringent tannins and other phenolic acids.

Most clinical research uses the essential oil, whose chemistry differs from that of the leaf tea.

Constituent Summary

European Pharmacopoeia limits for steam-distilled peppermint oil ^{33Reference 33European Directorate for the Quality of et al.European Pharmacopoeia — Peppermint oil (Menthae piperitae aetheroleum): gas-chromatographic composition limits}.

Pharmacology & Research

Peppermint oil has been tested in many human trials, most of them for digestive disorders. Enteric-coated or sustained-release oil has been pooled in several meta-analyses for irritable bowel syndrome ^{1,2,3,4Reference 1Ingrosso et al. · 2022Meta-analysisSystematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome — systematic review, meta-analysisView study →Reference 2Ford et al. · 2008Meta-analysisEffect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →Reference 3Khanna et al. · 2014Meta-analysisPeppermint oil for the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →Reference 4Alammar et al. · 2019Meta-analysisThe impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data — meta-analysisView study →}. A fixed peppermint and caraway oil combination has its own trials for functional dyspepsia ^{11,12,13,14Reference 11May et al. · 2000RCTEfficacy and tolerability of a fixed combination of peppermint oil and caraway oil in patients suffering from functional dyspepsia — randomised controlled trialView study →Reference 12Holtmann et al. · 2003RCTEffects of a fixed combination of peppermint oil and caraway oil on symptoms and quality of life in patients suffering from functional dyspepsia — randomised controlled trialView study →Reference 13Rich et al. · 2017RCTA randomized placebo-controlled trial on the effects of Menthacarin, a proprietary peppermint- and caraway-oil-preparation, on symptoms and quality of life in patients with functional dyspepsia — randomised controlled trialView study →Reference 14Li et al. · 2019Meta-analysisA combination of peppermint oil and caraway oil for the treatment of functional dyspepsia: a systematic review and meta-analysis — systematic review, meta-analysisView study →}, and dilute oil is used to relax the gut during endoscopy ^{15,16,17Reference 15Yamamoto et al. · 2006Clinical trialEfficacy of peppermint oil as an antispasmodic during endoscopic retrograde cholangiopancreatography — clinical trialView study →Reference 16Aziz et al. · 2020Meta-analysisThe anti-spasmodic effect of peppermint oil during colonoscopy: a systematic review and meta-analysis — systematic review, meta-analysisView study →Reference 17Shavakhi et al. · 2012RCTPremedication with peppermint oil capsules in colonoscopy: a double blind placebo-controlled randomized trial study — randomised controlled trialView study →}.

Topical oil has been tested for tension headache ^{18,19Reference 18Göbel et al. · 1996RCTEffectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type — randomised controlled trialView study →Reference 19Göbel et al. · 2016ReviewPeppermint oil in the acute treatment of tension-type headache — reviewView study →}, and inhaled oil for nausea ^{25,26Reference 25Ahn et al. · 2024Meta-analysisEffects of aromatherapy on nausea and vomiting in patients with cancer: a systematic review and meta-analysis of randomized controlled trials — systematic review, meta-analysisView study →Reference 26Şancı et al. · 2023RCTEffect of peppermint-lemon aromatherapy on nausea-vomiting and quality of life in pediatric patients with leukemia: a randomized controlled trial — randomised controlled trialView study →}. The antimicrobial, antioxidant and anti-inflammatory work is preclinical ^{23,27,28Reference 23Sroka et al. · 2005In vitroAntiradical and anti-H2O2 properties of polyphenolic compounds from an aqueous peppermint extract — in vitroView study →Reference 27Saharkhiz et al. · 2012In vitroChemical composition, antifungal and antibiofilm activities of the essential oil of Mentha piperita L. — in vitroView study →Reference 28Taher · 2012AnimalAntinociceptive activity of Mentha piperita leaf aqueous extract in mice — animal modelView study →}.

1. Irritable Bowel Syndrome

This is peppermint’s best-evidenced use. Enteric-coated or sustained-release peppermint oil capsules reduced global IBS symptoms and abdominal pain against placebo in several double-blind trials ^{6,7,8,9Reference 6Cappello et al. · 2007RCTPeppermint oil (Mintoil) in the treatment of irritable bowel syndrome: a prospective double blind placebo-controlled randomized trial — randomised controlled trialView study →Reference 7Merat et al. · 2010RCTThe effect of enteric-coated, delayed-release peppermint oil on irritable bowel syndrome — randomised controlled trialView study →Reference 8Cash et al. · 2016RCTA novel delivery system of peppermint oil is an effective therapy for irritable bowel syndrome symptoms — randomised controlled trialView study →Reference 9Liu et al. · 1997RCTEnteric-coated peppermint-oil capsules in the treatment of irritable bowel syndrome — randomised controlled trialView study →}.

Several meta-analyses pool this into a consistent benefit. A 2008 BMJ review of four trials (392 patients) found peppermint oil better than placebo ^{2Reference 2Ford et al. · 2008Meta-analysisEffect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →}. Khanna (2014; 9 trials, 726 patients) and Alammar (2019; 12 trials, 835 patients) reached the same conclusion, with numbers needed to treat of 3 for global symptoms and 4 for abdominal pain in the later review ^{3,4Reference 3Khanna et al. · 2014Meta-analysisPeppermint oil for the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →Reference 4Alammar et al. · 2019Meta-analysisThe impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data — meta-analysisView study →}.

The 2022 update by Ingrosso (10 trials, 1,030 patients) found numbers needed to treat of 4 for global symptoms and 7 for abdominal pain. Adverse events were more frequent than on placebo, and the quality of the evidence was rated very low ^{1Reference 1Ingrosso et al. · 2022Meta-analysisSystematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome — systematic review, meta-analysisView study →}.

The largest single trial (Weerts 2020, 190 patients, 182 mg capsules for 8 weeks) missed its primary endpoints of abdominal pain response and overall relief. The small-intestinal-release capsule did improve abdominal pain, discomfort and IBS severity as secondary outcomes ^{5Reference 5Weerts et al. · 2020RCTEfficacy and safety of peppermint oil in a randomized, double-blind trial of patients with irritable bowel syndrome — randomised controlled trialView study →}.

The mechanism is antispasmodic: menthol and peppermint oil block calcium channels in intestinal smooth muscle, relaxing it ^{21,22Reference 21Hills et al. · 1991In vitroThe mechanism of action of peppermint oil on gastrointestinal smooth muscleView study →Reference 22Hawthorn et al. · 1988In vitroThe actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations — in vitroView study →}.

In a trial of 42 children with IBS, 75% of those on enteric-coated peppermint oil had less severe pain after 2 weeks ^{20Reference 20Kline et al. · 2001RCTEnteric-coated, pH-dependent peppermint oil capsules for the treatment of irritable bowel syndrome in children — randomised controlled trialView study →}. In 30 children with functional abdominal pain, a week of peppermint oil left the overall gut microbiome unchanged, altering only a few low-abundance bacteria ^{30Reference 30Thapa et al. · 2022Peppermint oil effects on the gut microbiome in children with functional abdominal pain — controlled studyView study →}.

Gap: trials are heterogeneous in formulation, dose and duration, follow-up is usually short (2–12 weeks), and long-term efficacy and relapse rates are largely untested.

2. Functional Dyspepsia

In functional dyspepsia, peppermint oil has been tested almost entirely as half of a fixed combination with caraway oil (marketed as Menthacarin/Enteroplant), not on its own.

In a trial of 96 outpatients, capsules of 90 mg peppermint oil and 50 mg caraway oil taken twice daily for 28 days reduced pain intensity by 40%, against 22% on placebo ^{11Reference 11May et al. · 2000RCTEfficacy and tolerability of a fixed combination of peppermint oil and caraway oil in patients suffering from functional dyspepsia — randomised controlled trialView study →}. A second placebo-controlled trial, in 114 outpatients over 4 weeks, found the combination improved pain, discomfort and quality of life ^{13Reference 13Rich et al. · 2017RCTA randomized placebo-controlled trial on the effects of Menthacarin, a proprietary peppermint- and caraway-oil-preparation, on symptoms and quality of life in patients with functional dyspepsia — randomised controlled trialView study →}.

A 2019 meta-analysis of five trials (578 participants) found a significant benefit over placebo, with a number needed to treat of 3, though the evidence quality was low to very low ^{14Reference 14Li et al. · 2019Meta-analysisA combination of peppermint oil and caraway oil for the treatment of functional dyspepsia: a systematic review and meta-analysis — systematic review, meta-analysisView study →}.

The proposed mechanisms are smooth-muscle relaxation and changes in visceral sensitivity ^{10Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}.

Gap: the evidence is for the peppermint + caraway combination — it cannot be assumed to hold for peppermint oil alone, and the trials are dominated by a single proprietary preparation.

3. GI Antispasmodic (Endoscopy)

Applied directly to the gut, dilute peppermint oil relaxes smooth muscle during endoscopy. In 40 patients undergoing ERCP, 20 mL of a 1.6% or 3.2% peppermint oil solution sprayed around the duodenal papilla reduced duodenal movement, and the procedure was completed with peppermint alone in 37 of 39 patients. The comparison was with 16 earlier patients given glucagon ^{15Reference 15Yamamoto et al. · 2006Clinical trialEfficacy of peppermint oil as an antispasmodic during endoscopic retrograde cholangiopancreatography — clinical trialView study →}.

A 2020 meta-analysis of six colonoscopy studies found less colonic spasm with peppermint oil, though the results varied widely between studies ^{16Reference 16Aziz et al. · 2020Meta-analysisThe anti-spasmodic effect of peppermint oil during colonoscopy: a systematic review and meta-analysis — systematic review, meta-analysisView study →}. In a double-blind trial of 65 patients, enteric-coated capsules taken 4 hours before colonoscopy shortened the procedure and reduced spasm and pain ^{17Reference 17Shavakhi et al. · 2012RCTPremedication with peppermint oil capsules in colonoscopy: a double blind placebo-controlled randomized trial study — randomised controlled trialView study →}.

This is the same menthol calcium-channel mechanism as in IBS, applied once rather than over weeks. It is a procedural aid rather than a treatment.

4. Tension Headache

In a double-blind crossover trial of 41 patients treating 164 headache attacks, a 10% peppermint oil solution in ethanol, applied to the forehead and temples and repeated after 15 and 30 minutes, reduced headache intensity from 15 minutes onward. Its effect did not differ significantly from 1,000 mg of paracetamol ^{18Reference 18Göbel et al. · 1996RCTEffectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type — randomised controlled trialView study →}.

A later review notes that 10% peppermint oil solutions are licensed for tension-type headache in adults and children over six ^{19Reference 19Göbel et al. · 2016ReviewPeppermint oil in the acute treatment of tension-type headache — reviewView study →}.

The proposed mechanism is menthol acting on cold-sensing TRP channels in the skin ^{10Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}. The trials come mainly from one research group, and the effect is for topical oil, not oral or tea use.

5. Antioxidant

Peppermint’s water-soluble phenolics are strong radical scavengers in vitro. In an aqueous leaf extract, eriocitrin, luteolin-7-O-rutinoside and rosmarinic acid had the strongest activity against DPPH radicals, and eriocitrin the strongest against hydrogen peroxide ^{23Reference 23Sroka et al. · 2005In vitroAntiradical and anti-H2O2 properties of polyphenolic compounds from an aqueous peppermint extract — in vitroView study →}.

A mouse study reporting radioprotective antioxidant activity against gamma irradiation was retracted in 2007 and is not counted here ^{24Reference 24Samarth et al. · 2006AnimalRadioprotective influence of Mentha piperita (Linn) against gamma irradiation in mice: antioxidant and radical scavenging activity — animal modelView study →}.

These findings stop at biochemical endpoints. No human study links peppermint intake to an antioxidant clinical outcome.

6. Nausea & Vomiting

Inhaled peppermint oil is widely used for nausea. A 2024 meta-analysis of 25 randomised trials of aromatherapy in adults with cancer found reduced nausea, with peppermint oil among the most successful oils, though the authors judged the evidence not yet conclusive ^{25Reference 25Ahn et al. · 2024Meta-analysisEffects of aromatherapy on nausea and vomiting in patients with cancer: a systematic review and meta-analysis of randomized controlled trials — systematic review, meta-analysisView study →}.

In 90 children aged 2–12 having chemotherapy, a peppermint and lemon oil blend inhaled from a diffuser improved nausea scores and quality of life compared with water vapour or no treatment ^{26Reference 26Şancı et al. · 2023RCTEffect of peppermint-lemon aromatherapy on nausea-vomiting and quality of life in pediatric patients with leukemia: a randomized controlled trial — randomised controlled trialView study →}.

Many trials combine peppermint with other oils or add it to antiemetic drugs, which makes its own contribution hard to separate. The trials are small, and an aroma is hard to blind.

7. Antimicrobial

Peppermint essential oil inhibited a range of fungi in vitro at 0.12–8.0 μL/mL and blocked biofilm formation by Candida albicans and C. dubliniensis ^{27Reference 27Saharkhiz et al. · 2012In vitroChemical composition, antifungal and antibiofilm activities of the essential oil of Mentha piperita L. — in vitroView study →}.

All the data are in vitro, at oil concentrations far above what oral or topical use delivers, and there is no clinical antimicrobial evidence.

8. Anti-Inflammatory & Analgesic

In mice, an aqueous peppermint leaf extract injected at 200 and 400 mg/kg reduced acetic-acid writhing by about 52% and raised the hot-plate pain threshold. It had no effect on carrageenan paw swelling, so the pain relief was not through an anti-inflammatory action ^{28Reference 28Taher · 2012AnimalAntinociceptive activity of Mentha piperita leaf aqueous extract in mice — animal modelView study →}.

The cooling pain relief of the topical oil is attributed to menthol acting on cold-sensing TRP channels ^{10Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}. Apart from topical use for headache, there is no controlled human trial of peppermint for pain or inflammation.

Mechanisms

Menthol has been studied at two main targets. It blocks L-type calcium channels in gut smooth muscle, which relaxes it ^{21,22Reference 21Hills et al. · 1991In vitroThe mechanism of action of peppermint oil on gastrointestinal smooth muscleView study →Reference 22Hawthorn et al. · 1988In vitroThe actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations — in vitroView study →}, and it acts on transient receptor potential (TRP) channels, including those that sense cold ^{10Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}.

The leaf’s water-soluble flavonoids and rosmarinic acid have been studied separately, as radical scavengers ^{23Reference 23Sroka et al. · 2005In vitroAntiradical and anti-H2O2 properties of polyphenolic compounds from an aqueous peppermint extract — in vitroView study →}.

Clinical Trials

ClinicalTrials.gov lists roughly 130 registered studies of peppermint oil, most of them in gastroenterology, and dozens of published trials have been pooled in meta-analyses for IBS and functional dyspepsia.

Last checked: July 2026.

Dosage

Clinical doses are for the essential oil, not the leaf.

Traditional Dosage

Safety & Pregnancy

Peppermint is well tolerated as a food and at trial doses. The main issues are heartburn from menthol, and keeping the oil away from young children’s faces.

Full Safety & Interactions Detail

Tolerability. Peppermint is well tolerated as a food and at the doses used in trials ^{10Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}. In IBS trials, side effects were more common on peppermint oil than on placebo, but they were mild and transient ^{1,3Reference 1Ingrosso et al. · 2022Meta-analysisSystematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome — systematic review, meta-analysisView study →Reference 3Khanna et al. · 2014Meta-analysisPeppermint oil for the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →}.

Heartburn and reflux. Heartburn is the most commonly reported side effect of the oil ^{3Reference 3Khanna et al. · 2014Meta-analysisPeppermint oil for the treatment of irritable bowel syndrome — systematic review, meta-analysisView study →}. Menthol relaxes the lower esophageal sphincter, so people with reflux or hiatus hernia should use peppermint with care, or use enteric-coated capsules, which release the oil past the stomach ^{5,10Reference 5Weerts et al. · 2020RCTEfficacy and safety of peppermint oil in a randomized, double-blind trial of patients with irritable bowel syndrome — randomised controlled trialView study →Reference 10Chumpitazi et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →}.

Young children. Peppermint oil should not be applied to the face or chest of infants and young children, because menthol can trigger reflex apnea.

Liver. Two minor constituents of the oil, pulegone and menthofuran, are toxic to the liver at high doses. The European Pharmacopoeia limits pulegone to 4% and menthofuran to 1–9% of the oil ^{33Reference 33European Directorate for the Quality of et al.European Pharmacopoeia — Peppermint oil (Menthae piperitae aetheroleum): gas-chromatographic composition limits}, and prolonged high-dose use of the oil is best avoided.

Allergy and iron. Allergic and contact reactions to menthol occur but are rare. The leaf’s tannins can modestly reduce iron absorption, so leaf preparations are best taken apart from iron-rich meals or supplements.

Interactions. In 12 healthy volunteers, a single 600 mg dose of peppermint oil raised blood levels of the blood-pressure drug felodipine by about 40%, which points to inhibition of the liver and gut enzyme CYP3A4 ^{37Reference 37Dresser et al. · 2002RCTEvaluation of peppermint oil and ascorbyl palmitate as inhibitors of cytochrome P4503A4 activity in vitro and in vivo — randomised crossover pharmacokinetic studyView study →}. Menthol on its own did not markedly change felodipine levels in 10 healthy volunteers ^{38Reference 38Gelal et al. · 2005Effect of menthol on the pharmacokinetics and pharmacodynamics of felodipine in healthy subjects — pharmacokinetic studyView study →}.

In mice, menthol raised liver CYP2C and lowered blood levels and the anticoagulant effect of warfarin ^{39Reference 39Hoshino et al. · 2014AnimalMenthol reduces the anticoagulant effect of warfarin by inducing cytochrome P450 2C expression — animal modelView study →}. Take care combining the oil capsules with felodipine and similar drugs, or with warfarin.

References

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