Peppermint oil

What it is

Peppermint is a hybrid mint and peppermint oil is the essential oil taken from the flowering parts and leaves of that plant. Essential oils are concentrated plant oils carrying the compounds that give a plant its odour and flavour; in peppermint oil the dominant one is menthol. It has been used for digestive complaints since antiquity and is sold today mainly as enteric-coated capsules.

What the research says

The best-quantified use is irritable bowel syndrome, where a 2022 meta-analysis of ten randomised trials found peppermint oil beat placebo for global symptoms and abdominal pain but rated the evidence very low quality by GRADE and found significantly more adverse events. The largest single trial, powered to regulator-defined endpoints, missed its primary endpoint. Proposed mechanisms include menthol blocking calcium channels and relaxing gut smooth muscle, but that is pharmacology, not proof of clinical benefit.

Evidence grade: Limited evidence.

What goes wrong

That same trial found peppermint oil produced more adverse events than placebo in both active arms. (Source 1)

• Randomized trial, Moderate certainty.
• Size: 189 patients in the intention-to-treat analysis.
• Who: Adults with Rome IV IBS.
• How long: 8 weeks.
• Result: P < .005 for adverse events in both peppermint oil groups versus placebo; events described as mild.
• Funding: not stated.

Limit of this finding: These adverse events come from the same trial that failed its primary endpoint, so the trial recorded more side effects on peppermint oil than on placebo without showing a benefit on the outcome it set out to measure.

Adverse events, although mild, were more common in both peppermint oil groups (P < .005).

Pooled across randomised trials, any adverse event was significantly more common on peppermint oil than placebo. (Source 2)

• Meta-analysis, Very low certainty.
• Size: 10 randomised controlled trials, 1030 patients.
• Who: Adults with irritable bowel syndrome.
• How long: not stated.
• Result: RR of any adverse event 1.57 (95% CI 1.04-2.37)
• Funding: not stated.

Adverse event rates were significantly higher with peppermint oil (RR of any adverse event = 1.57; 95% CI 1.04-2.37).

In the same review, symptoms of gastro-oesophageal reflux were reported by 17.9% of patients on peppermint oil against 7.7% on placebo, a number needed to harm of about 20. (Source 3)

• Meta-analysis, Very low certainty.
• Size: 8 randomised controlled trials; 465 patients randomised to peppermint oil and 444 to placebo.
• Who: Adults with irritable bowel syndrome in randomised trials that reported gastro-oesophageal reflux symptoms.
• How long: not stated.
• Result: Reflux symptoms 83/465 (17.9%) vs 34/444 (7.7%); RR 1.67 (95% CI 1.18 to 2.38); NNH 19.5 (95% CI 9.5 to 72.5)
• Funding: not stated.

Limit of this finding: These figures are for heartburn-type reflux symptoms specifically, not for side effects of every kind; the review reports any adverse event separately as 58 of 340 on peppermint oil against 46 of 380 on placebo. The review also says eight trials with 973 patients supplied the reflux data, yet the counts it prints add up to 909 people (465 plus 444) and it does not explain the difference, so read the percentages as rates among the patients actually counted.

These were reported by 83 (17.9%) of 465 patient randomised to peppermint oil, versus 34 (7.7%) of 444 patients receiving placebo (RR = 1.67; 95% CI 1.18 to 2.38, NNH = 19.5; 95% CI 9.5 to 72.5) (Figure 6).

The European Medicines Agency's herbal monograph records heartburn, dry mouth, nausea and vomiting as frequent in clinical trials of oral peppermint oil, and rare allergic reactions including anaphylactic shock. (Source 4)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: Users of authorised peppermint oil medicinal products.
• How long: not applicable.
• Result: Frequency of allergic reactions stated as not known; gastrointestinal effects described as frequent in clinical trials.
• Funding: not stated.

Heartburn, perianal burning blurred vision, dry mouth, nausea and vomiting were frequent in clinical trials.

The European Medicines Agency contraindicates oral peppermint oil in people with biliary and liver disorders, and in children under two because menthol can trigger reflex apnoea and laryngospasm. (Source 5)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: People with liver, gallbladder or biliary disease; infants and young children.
• How long: not applicable.
• Result: Absolute contraindications listed in the monograph, no rate given.
• Funding: not stated.

Patients with liver disease, cholangitis, achlorhydria, gallstones and any other biliary disorders.

A published case report documents IgE-mediated anaphylaxis to peppermint after sucking a peppermint sweet, requiring intramuscular epinephrine. (Source 6)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: 69-year-old man with no prior food or drug allergy.
• How long: Onset within five minutes of exposure.
• Result: Lip and tongue swelling, throat tightness, shortness of breath, progressing to cough, wheeze and difficulty swallowing; skin prick test strongly positive, negative in five healthy controls.
• Funding: not stated.

A 69 year old male developed sudden onset of lip and tongue swelling, throat tightness and shortness of breath within five minutes of sucking on a peppermint candy.

NCCIH's position (last updated May 2025) is that peppermint oil appears safe at commonly used doses, with heartburn among the possible oral side effects, and that enteric coating is used to reduce heartburn. (Source 7)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: General adult users.
• How long: not applicable.
• Result: No rates given; long-term safety of large amounts of peppermint leaf described as unknown.
• Funding: not stated.

Possible side effects of peppermint oil taken orally include heartburn, nausea, abdominal pain, and dry mouth.

What the evidence supports

In a 2022 systematic review and meta-analysis of randomised trials, peppermint oil was better than placebo for global IBS symptoms and abdominal pain, but the pooled evidence was graded very low quality. (Source 2)

• Meta-analysis, Very low certainty.
• Size: 10 randomised controlled trials, 1030 patients.
• Who: Adults meeting diagnostic criteria for irritable bowel syndrome.
• How long: Trials of short duration; search to 2 April 2022.
• Result: RR of global symptoms not improving 0.65 (95% CI 0.43-0.98), NNT = 4 (95% CI 2.5-71); RR of abdominal pain not improving 0.76 (95% CI 0.62-0.93), NNT = 7 (95% CI 4-24)
• Funding: not stated.

Peppermint oil was more efficacious than placebo for global IBS symptoms (RR of symptoms not improving = 0.65; 95% CI 0.43-0.98, number needed to treat (NNT) = 4; 95 % CI 2.5-71), and abdominal pain (RR of abdominal pain not improving = 0.76; 95% CI 0.62-0.93, NNT = 7; 95 % CI 4-24).

The American College of Gastroenterology issued a conditional recommendation for peppermint in IBS on low quality evidence (position, January 2021). (Source 8)

• Official position, Low certainty.
• Size: not applicable.
• Who: Adults with irritable bowel syndrome.
• How long: not applicable.
• Result: Conditional recommendation; low quality of evidence.
• Funding: not stated.

We suggest the use of peppermint to provide relief of global IBS symptoms. Conditional recommendation; low quality of evidence.

What the evidence does not support

In the largest randomised trial of peppermint oil in IBS, neither small-intestinal-release nor ileocolonic-release peppermint oil met the regulator-defined primary endpoint for abdominal pain response or the co-primary endpoint of overall symptom relief. (Source 1)

• Randomized trial, Moderate certainty.
• Size: 190 randomised, 189 in the intention-to-treat analysis.
• Who: Adults meeting Rome IV criteria for IBS at four Dutch hospitals, mean age 34.0 years, 77.8% female.
• How long: 8 weeks.
• Result: Abdominal pain response 46.8% small-intestinal-release (P = .170 vs placebo), 41.3% ileocolonic-release (P = .385), 34.4% placebo; overall relief 9.7% (P = .317) and 1.6% (P = .351) vs 4.7% placebo.
• Funding: not stated.

Limit of this finding: This trial was negative on the endpoints it was designed to test. It did report improvements on secondary measures of abdominal pain, discomfort and symptom severity, but secondary results from a trial that missed its primary endpoint are exploratory and cannot stand in for a positive result. The authors' own conclusion was that the findings do not support further development of the ileocolonic-release form.

In a randomized trial of patients with IBS, we found that neither small-intestinal-release nor ileocolonic-release peppermint oil (8 weeks) produced statistically significant reductions in abdominal pain response or overall symptom relief, when using US Food and Drug Administration/European Medicines Agency recommended endpoints.

Where the evidence is mixed

The same review's authors judged the certainty of that benefit as very low because of inconsistency, possible publication bias and few trials at low risk of bias. (Source 9)

• Meta-analysis, Very low certainty.
• Size: 10 randomised controlled trials, 1030 patients.
• Who: Adults with irritable bowel syndrome.
• How long: not stated.
• Result: GRADE rating of very low; only three included RCTs were at low risk of bias.
• Funding: not stated.

As a result, and by GRADE criteria, the quality of evidence would be judged as very low.

The meta-analysis the ACG relied on found adverse events statistically no different from placebo, which conflicts with the later 2022 pooled estimate. (Source 10)

• Official position, Low certainty.
• Size: 8 RCTs for the adverse event analysis, within a review of 12 RCTs and 835 patients.
• Who: Adults with irritable bowel syndrome.
• How long: Included trials 2-12 weeks.
• Result: AEs 9.3% vs 6.1%, RR 1.40 (95% CI 0.87-2.26), P = 0.16.
• Funding: not stated.

In 8 RCTs, AEs were similar between peppermint oil and placebo (9.3% vs 6.1%, respectively; RR 1.40; 95% CI 0.87-2.26; P = 0.16) (147).

Where the research disagrees

Whether peppermint oil causes more adverse events than placebo in IBS trials

• American College of Gastroenterology guideline, 2021, citing an earlier meta-analysis, position citing meta-analysis: In 8 RCTs, AEs were similar between peppermint oil and placebo (9.3% vs 6.1%, respectively; RR 1.40; 95% CI 0.87-2.26; P = 0.16) (147). (Source 10)
• Alimentary Pharmacology and Therapeutics systematic review and meta-analysis, 2022, meta-analysis: Adverse event rates were significantly higher with peppermint oil (RR of any adverse event = 1.57; 95% CI 1.04-2.37). (Source 2)

How much

• Reference intake: No reference intake (RDA or AI) exists for peppermint oil because it is not a nutrient; it is promoted as a remedy rather than eaten for nutritional need. NCCIH, position last updated May 2025. (Source 11)
• Upper limit: No tolerable upper intake level or acceptable daily intake was identified in the sources reached. NCCIH states only that the oil appears safe at doses commonly used, and the EMA monograph sets a permitted daily dose for authorised products rather than a safety ceiling for supplements. (Source 7)
• Studied: The Dutch PERSUADE trial gave 182 mg of small-intestinal-release or ileocolonic-release peppermint oil, or placebo, for 8 weeks. (Source 1)
• Studied: The trials pooled in the ACG guideline's source meta-analysis ranged from 18 to 178 patients and ran 2 to 12 weeks, all with continuous rather than as-needed dosing. (Source 10)

A common belief, and what the research shows

The belief: Peppermint oil is a gentle herbal remedy with no real side effects, so enteric coating is just a marketing detail.

What the research shows: Pooled trial data show significantly more adverse events on peppermint oil than placebo, and the EMA lists heartburn, dry mouth, nausea and vomiting as frequent in trials, with rare anaphylactic shock. The coating exists precisely to limit reflux: NCCIH states that 'Capsules containing peppermint oil are often enteric-coated to reduce the likelihood of heartburn.' The 2022 meta-analysis states that 'Adverse event rates were significantly higher with peppermint oil (RR of any adverse event = 1.57; 95% CI 1.04-2.37).'

Questions and answers

What is it?

Peppermint is a natural cross between water mint and spearmint. Peppermint oil is the concentrated essential oil distilled from the flowering parts and leaves of that plant, and its main active compound is menthol. It is sold as capsules, liquids and topical preparations. (Source 11)

What does it do in the body?

Inside the gut, menthol is thought to block calcium channels in smooth muscle, relaxing the bowel wall. Other proposed actions include effects on visceral sensation via transient receptor potential channels, and direct antimicrobial and anti-inflammatory effects. These are mechanistic explanations, not demonstrated clinical effects. (Source 8)

Is it good or bad for you?

For adults with irritable bowel syndrome the pooled trial evidence points to a modest symptom benefit, but the reviewers rated that evidence very low quality and found adverse events more common than on placebo. The largest single trial missed its primary endpoints. It is best described as a possibly helpful short-term symptomatic option with a real side effect cost, not a proven treatment. (Source 2)

How do you get more of it?

In trials people took it as capsules at fixed doses. The largest IBS trial used 182 mg of peppermint oil in a release-targeted capsule, taken for eight weeks. Trials in the guideline evidence base all used continuous rather than as-needed dosing. (Source 1)

If it is harmful, what reduces it?

Peppermint oil is not stored in the body, so there is nothing to clear; the exposure ends when the capsules stop. Where the problem is reflux or heartburn from the oil releasing too early, formulation is the lever the literature describes, with enteric coating used specifically to lower that risk. (Source 7)

Why might someone be low in it or missing it?

Does not apply. Peppermint oil is not a nutrient and there is no deficiency state; nobody is low in it. People simply either take it as a promoted remedy or they do not. (Source 11)

Which whole foods contain it or feed it?

Peppermint leaf is eaten and drunk as a herb and as tea, and NCCIH describes peppermint tea as appearing safe, though the long-term safety of large amounts of the leaf is unknown. Tea is not the same preparation as the concentrated oil used in IBS trials, and the trial evidence does not transfer to it. (Source 7)

What happens if you do not have it?

Nothing is lost by not taking it, because it is not essential to the body. Its only established role is as an optional symptomatic treatment that a gastroenterology guideline suggests conditionally, on low quality evidence, for irritable bowel syndrome. (Source 8)

How can you test for it?

There is no clinical test for peppermint oil status, and none is described in the reviews and guidelines we reached. The only assessment used in the literature is symptom response measured in trials, using endpoints such as the FDA abdominal pain responder definition. (Source 7)

We searched: Searched the 2022 Alimentary Pharmacology and Therapeutics meta-analysis, the 2021 ACG IBS guideline, the EMA herbal monograph on Mentha x piperita aetheroleum and the NCCIH peppermint oil page for any biomarker, blood level or diagnostic test; none is described.

References

1. Gastroenterology (record held at Maastricht University CRIS). Efficacy and Safety of Peppermint Oil in a Randomized, Double-Blind Trial of Patients With Irritable Bowel Syndrome. 2020. PMID 31470006, DOI 10.1053/j.gastro.2019.08.026. Read the source
2. Alimentary Pharmacology & Therapeutics (author accepted manuscript, White Rose Research Online). Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome. 2022. DOI 10.1111/apt.17179. Read the source
3. Alimentary Pharmacology & Therapeutics (author accepted manuscript, White Rose Research Online). Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome (gastro-oesophageal reflux symptoms). 2022. DOI 10.1111/apt.17179. Read the source
4. European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Mentha x piperita L., aetheroleum - Revision 1 (Undesirable effects). 2020. Read the source
5. European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Mentha x piperita L., aetheroleum - Revision 1 (Contraindications). 2020. Read the source
6. Allergy, Asthma & Clinical Immunology. A case of anaphylaxis to peppermint. 2014. PMID 24472564, DOI 10.1186/1710-1492-10-6. Read the source
7. National Center for Complementary and Integrative Health, NIH. Peppermint Oil: Usefulness and Safety (Safety). 2025. Read the source
8. American Journal of Gastroenterology / American College of Gastroenterology. ACG Clinical Guideline: Management of Irritable Bowel Syndrome (peppermint recommendation). 2021. PMID 33315591, DOI 10.14309/ajg.0000000000001036. Read the source
9. Alimentary Pharmacology & Therapeutics (author accepted manuscript, White Rose Research Online). Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome (Discussion, quality of evidence). 2022. DOI 10.1111/apt.17179. Read the source
10. American Journal of Gastroenterology / American College of Gastroenterology. ACG Clinical Guideline: Management of Irritable Bowel Syndrome (peppermint evidence summary). 2021. PMID 33315591, DOI 10.14309/ajg.0000000000001036. Read the source
11. National Center for Complementary and Integrative Health, NIH. Peppermint Oil: Usefulness and Safety (Background). 2025. Read the source