What is peppermint oil good for?

Peppermint is a hybrid mint, a cross between two types of mint water mint [Mentha aquatica] and spearmint [Mentha spicata L.] also known as Mentha piperita. Indigenous to Europe and the Middle East, the plant is now widespread in cultivation in many regions of the world 1. Peppermint has been used for health purposes for several thousand years. It is mentioned in records from ancient Greece, Rome, and Egypt. Peppermint oil is obtained by steam distillation from the fresh leaves of peppermint 2. Both peppermint leaves and peppermint essential oil from peppermint have been used for health purposes. However, peppermint was not recognized as a distinct kind of mint until the 1700s. Essential oils are very concentrated oils containing substances that give a plant its characteristic odor or flavor. Peppermint is a common flavoring agent in foods, and peppermint oil is used to create a pleasant fragrance in soaps and cosmetics. Today, peppermint is promoted for irritable bowel syndrome (IBS), other digestive problems, the common cold, sinus infections, headaches, and other conditions. Peppermint oil is promoted for topical use (applied to the skin) for problems like headache, muscle aches, joint pain, and itching. In aromatherapy, peppermint oil is promoted for treating coughs and colds, reducing pain, improving mental function, and reducing stress.

Although results from clinical trials are mixed, the majority of evidence indicates that enteric-coated peppermint oil may be modestly effective in reducing some of the common symptoms of IBS. In combination with caraway oil, peppermint oil also may be effective in treating non-ulcer dyspepsia. Limited data show a modest effect at reducing colonic spasm during barium enema. Topical peppermint oil also may be helpful for treatment of tension headache. Peppermint oil should only be used at the recommended doses because significant toxicity can occur at higher doses. Even the recommended medicinal doses of peppermint oil should not be used in infants or very young children, or in women who are pregnant or lactating.

Peppermint oil contains a large number (> 80) of components including menthol (35–55%), l-menthone (20–31%), menthyl acetate (3–10%), cineol, and several other volatile oils (piperitenone carvone, menthofuran, isomenthone, isopulegol, 3-octanol, pulegone) 3. Peppermint oil major constituent and active ingredients appear to be menthol that in nature exists as a pure stereoisomer 4. Menthol activates cold-sensitive TRPM8 receptors in the skin and mucosal tissues, and is the primary source of the cooling sensation that follows the topical application of peppermint oil 5. Menthol is listed as generally regarded as safe (GRAS) by the US Food and Drug Administration 6. Peppermint oil has a high concentration of natural pesticides, mainly pulegone and menthone 7. It is known to repel some pest insects, including mosquitos, and has uses in organic gardening 7.

In addition, δ-cadinene, copaene, eugenol, methyl pivalate, menthomenthene, thujopsene, caryophyllene oxide also some of the compound identified in peppermint essential oil and demonstrated antifungal activity and antibacterial activity 8, 9. Peppermint essential oil have shown potent inhibitory activity against several microorganisms such as Penicillium digitatum, Aspergillus flavus, Aspergillus niger, Candida albicans, Saccharomyces cerevisiae Mucor spp., and Fusarium oxysporum 10. Peppermint oil has been reported as antifungal agent for several mycotoxigenic speceies by Silva et al. 11; Aspergillus flavus and Aspergillus parasiticus, Freire et al. 12, in 2012 reported against Aspergillus ochraceous, Colletotrichum gloeosporioides, Colletotrichum musae, F. oxysporum, Fusarium semitectum. Peppermint essential oil anti-inflammatory 13, antioxidant 14 and cytotoxic effects were reported by Sun et al. 15. Owing to the various constituents of peppermint, it has a variety uses, including topical application as an antiseptic and analgesic, inhalation as aromatherapy, and oral formulation for treatment of headache and various functional gastrointestinal disorders (FGIDs) such as irritable bowel syndrome (IBS). Currently, peppermint essential oil has been widely used in cosmetic, food and pharmaceutical industries.

Peppermint leaves are aromatic perennial herb cultivated in most part of the world and it is used as folk medicine and frequently used in herbal tea and for culinary purpose to add flavor and aroma 16. Today, peppermint is used as a dietary supplement for irritable bowel syndrome (IBS), other digestive problems, the common cold, headaches, and other conditions. Peppermint oil is also used topically (applied to the skin) for headache, muscle aches, itching, and other problems. Peppermint leaf is available in teas, capsules, and as a liquid extract. Peppermint oil is available as liquid solutions and in capsules, including enteric-coated capsules.

Peppermint tea, which is made from peppermint leaves, appears to be safe. However, the long-term safety of consuming large amounts of peppermint leaf is unknown.

Peppermint oil appears to be safe when taken orally (by mouth) or applied topically in the doses commonly used. Peppermint oil has been safely used in many clinical trials. However, like many essential oils, peppermint oil can be toxic and even lethal at excessive dosages; it has been associated with interstitial nephritis and acute renal failure 17. It may have a choleretic effect and is contraindicated in patients with cholelithiasis or cholecystitis. Peppermint oil is relatively contraindicated in patients with hiatal hernia or significant gastroesophageal reflux disease, because its effect on the lower esophageal sphincter can lead to exacerbation of symptoms.

Peppermint oil has been used to trigger menstruation and should be avoided during pregnancy. Little is known about whether it’s safe to use peppermint oil during pregnancy or while breastfeeding. Peppermint oil should not be used internally or on or near the face in infants and young children because of its potential to cause bronchospasm, tongue spasms, and, possibly, respiratory arrest 18. However, the amount of peppermint in over-the-counter medications, topical preparations, and herbal teas is likely safe in pregnant and lactating women and in young children.

Possible side effects of peppermint oil taken orally include heartburn, nausea, and vomiting, abdominal pain, perianal burning, blurred vision and dry mouth 19. Rarely, peppermint oil can cause allergic reactions. Capsules containing peppermint oil are often enteric-coated to reduce the likelihood of heartburn. If enteric-coated peppermint oil capsules are taken at the same time as antacids, the coating can break down too quickly. Preliminary evidence from laboratory studies suggests that peppermint leaf and peppermint oil may inhibit the cytochrome P450 1A2 system 20, which theoretically could lead to increased serum levels of drugs such as amitriptyline, cyclosporine (Sandimmune), and haloperidol (Haldol) in patients who regularly consume large amounts of peppermint leaf or peppermint oil. However, this interaction has not been proven to occur in humans. Peppermint oil has been reported to raise serum levels of simvastatin (Zocor) and felodipine (Plendil) in at least one case report 21.

Side effects of applying peppermint oil to the skin can include skin rashes and irritation. Peppermint oil should not be applied to the face of infants or young children because serious side effects may occur if they inhale the menthol in the oil.

Figure 1. Peppermint


Chemical Composition and Anti-Inflammatory, Cytotoxic and Antioxidant Activities of Peppermint Essential Oil from Leaves

51 volatile constituents in peppermint essential oil have been evaluated for their anti-inflammatory, cytotoxic and antioxidant activities 15. Test tube and animal studies showed that peppermint essential oil had a potent anti-inflammatory activity in the croton oil-induced mouse ear edema model, and the possible action mechanism might be attributed to its inhibitory effect on the production of nitric oxide (NO) and prostaglandin E2 (PGE2). Peppermint essential oil was also found to be active against SPC-A-1, K562 and SGC-7901 cancer cell lines. In addition, peppermint essential oil had a moderate antioxidant activity.

Peppermint antioxidant actions were previously suggested to be due to the presence of phenolic constituents in its leaves including rosmarinic acid and different flavonoids such as rutin, naringin, eriocitrin, luteolin, and hesperidin 22, 23. High-performance liquid chromatography (HPLC) analysis of the peppermint leaf hydroalcoholic extract detected some peaks that coeluted with pure ursolic acid, epicatechin, caffeic acid, rutin, quercetin, naringenin, and kaempferol. These compounds were previously shown to act as anti-inflammatory and/or antioxidants 24. In animal studies, it was clearly demonstrated in the Ames test that peppermint has antimutagenic effects once it significantly inhibited the shamma—a tobacco product—induced oral carcinogenesis in the hamster cheek pouch 25. These results may serve as valuable research references for clinical research of medicines for treatment of inflammation and cancer in the future.

Table 1. Chemical composition of peppermint essential oil

Molecular weightChemical constituents(%)
9154Terpineol, cis-,β-0.71
111542-Cyclohexen-1-ol, 1-methyl-4-(1-methylethyl)-, trans-0.07
16156Cyclohexanol, 5-methyl-2-(1-methylethyl)-, (1α, 2α, 5α)-0.45
22198Menthy acetate12.86
24196Isopuegyl acetate0.08
32204Naphthalene, 1,2,4a,5,6,8a-hexahydro-4,7-dimethyl-1-(1-methylethyl)-0.06
342042(4H)-Benzofuranone, 5,6,7,7a-tetrahydro-3,6-dimethyl-1.69
36154β-(3-Thienyl)acrylic acid2.09
38220Caryophyllene oxide1.37
42220Aristolene epoxide0.1
46220cis-Z-.α.-Bisabolene epoxide0.2
47268Hexahydrofarnesgl acetone0.15

aRetention time (min).
bKovats index relative to n-alkanes (C9–C25) on HP-1 capillary column.

[Source 15]

Peppermint essential oil benefits

In Eastern and Western traditional medicines, peppermint and its oil have been used in antispasmodics, aromatics, antiseptics or even medications for the treatment of colds, cramps, indigestions, nausea, sore throat, toothache or even cancer 26. Modern pharmacology research has demonstrated that peppermint possesses antioxidant, antitumor, antiallergenic, antiviral and antibacterial activities 27, 28, 29, 30.

Peppermint oil for IBS (Irritable Bowel Syndrome)

Irritable bowel syndrome (IBS) is a common condition with a community prevalence of 10-15% of the general population 31. The annual incidence in primary care is around 0.8%, and the prevalence of patients diagnosed in primary care is about 3-4% 32. IBS has no single identified cause. It is not a pathological condition, i.e. there is no underlying disease process, but the bowel does not function properly, causing discomfort and inconvenience for sufferers. The pathophysiology of IBS is complex and involves an interaction of various factors, which includes, but is not limited to, genetic predisposition, gut-brain axis, visceral sensitivity, gastrointestinal motility, gut dysbiosis, neurotransmitters, food reactions, intestinal permeability, bile acids, inflammatory mediators, early-life stressors, psychosocial maladaptation, and somatization, among others 33. IBS is difficult to treat, hence the wide range of treatments used—dietary exclusion, fiber supplements, and probiotics; antispasmodic drugs, antidiarrhoeal agents, and laxatives; antidepressants, hypnotherapy, and cognitive behavioral therapy. IBS patients with mild and intermittent symptoms usually benefit from lifestyle and dietary modification, which includes a diet low in fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) 34; and in some cases, lactose and gluten avoidance 35. Smooth muscle relaxants and antispasmodics can also be used to help with IBS symptoms, especially abdominal pain and bloating 36.

Although results of studies on the use of peppermint oil for the treatment of IBS symptoms have been mixed 37, there seems to be a trend indicating mild effectiveness in the reduction of some IBS symptoms, especially flatulence and abdominal pain and distension.

In this systematic review and meta-analysis 38, the researchers investigated the effectiveness of antispasmodics, fiber and peppermint oil in the treatment of IBS (irritable bowel syndrome). Individual trials on these treatments have been of variable quality with conflicting results, and previous systematic reviews have also resulted in different conclusions. This is a high quality systematic review that looked into all published research of peppermint oil, muscle relaxants (or antispasmodics) and fiber used in the treatment of IBS (irritable bowel syndrome). The three treatments were all found to reduce the risk of having persistent symptoms (such as abdominal pain and bloating) compared to placebo.

The researchers searched medical research databases to identify all randomized controlled trials (including foreign language studies) involving adults who met diagnostic criteria for IBS and who had received investigations, if necessary, to exclude an underlying cause. Studies had to compare antispasmodics, fibre or peppermint oil with an inactive placebo drug. They also had to include a follow-up of at least one week with an assessment of cure or improvement of symptoms. The researchers also hand-searched abstracts of conference proceedings for potential studies and looked at reference lists of all selected studies.

The main outcome that the researchers looked for was the efficacy of any of the three treatments compared to placebo on all IBS symptoms or just abdominal pain. The researchers assessed the quality of the trials and results were pooled to give the relative risk of symptoms persisting after treatment.

The search found 35 eligible studies for inclusion: 19 involving antispasmodics, nine of fibre, four of peppermint oil, and three involving antispasmodics or fibre.

The 12 trials of fiber had a total of 591 people with IBS. Treatments included bran (five studies), ispaghula husk (six studies) and, in one study, concentrated fiber. Overall, any fiber treatment reduced the risk of persistent symptoms by 13%, but this result was only of borderline significance. The only individual treatment that gave a significant reduction in symptoms was ispaghula.

The 22 trials of antispasmodics included 1,778 people with IBS and used a variety of drugs (12 in total) at different doses. Overall, antispasmodics significantly reduced the risk of persistent symptoms by 32% 38. Of the individual drugs, only hyoscine, cimetropium, pinaverium and otilonium gave consistent significant evidence of benefit.

The four trials of peppermint oil, at different doses, included 392 people with IBS. Across these studies, 26% of those randomized to peppermint oil experienced persistent symptoms compared to 65% of those assigned to placebo. This gave an overall 57% reduction in risk of persistent symptoms when taking peppermint oil 38.

The number of people that would need to be treated to prevent one person from having persistent abdominal symptoms was 2.5 for peppermint, five for antispasmodics and 11 for fiber 38. This review provides evidence to support the use of symptomatic treatments such as peppermint oil 38.

However, there are several points to bear in mind:

  • The trials included in the review were of variable size, included slightly different patient groups, fulfilling different diagnostic criteria for IBS, different doses and treatment durations, were carried out in different settings (e.g. primary or secondary care), and used different criteria for symptom improvement. In the antispasmodic and peppermint oil trials, heterogeneity (diversity) was demonstrated to be statistically significant, i.e. different methods and results were obtained between trials, which may call into question the validity of combining results of the studies in this way.
  • Although peppermint oil was highlighted in the review, as it demonstrated the greatest reduction in risk, it only included four trials with 392 people. This limits the strength of the conclusions that can be drawn from the combination of these studies. However, this is partly countered by the fact that three of the studies were of high quality and there was no statistical heterogeneity when they were combined. This increases the confidence in the finding.
  • The authors report that none of the trials state whether the allocation of the treatments was concealed. This means that practitioners may have been aware of whether the active treatment or placebo was being given to participants. It has been found that this type of bias may give an overestimation of treatment effect.
  • Adverse effects were not consistently reported across studies, so no firm conclusions can be made about the safety of any of the three treatments.
  • The trials have only compared each treatment to inactive placebo, so it cannot be assumed that any one treatment is more effective than the others.

A prospective, double blind, placebo-controlled randomized trial with 57 patients with IBS by Rome II criteria showed that 64% of patients receiving enteric-coated peppermint oil and 34% of placebo users experienced a reduction in the total IBS symptom score at 4 weeks of ≥50% in the intention-to-treat population 39. They also assessed the symptom score at 4 weeks after the end of treatment (8 weeks) and found a persisting beneficial effect at 8 weeks. Another randomized double-blind placebo-controlled study on 90 outpatients with IBS by Rome II criteria was conducted to demonstrate the efficacy of peppermint oil on quality of life 40. Patients were randomly assigned to receive one capsule of Colpermin® (Tillotts Pharma, Ziefen, Switzerland) or a placebo three times daily for 8 weeks. They examined the effectiveness of peppermint oil in terms of relieving symptoms and improving quality of life using a questionnaire addressing six IBS symptoms and the 36-item Short Form Health Survey (SF-36) for quality of life. At week 8, 42.5% of patients receiving peppermint oil and 22.2% of patients receiving placebo were free from abdominal pain or discomfort 40. However, there were no significant between-group differences detected in other IBS symptoms such as abdominal distension, flatulence, loose stool, hard stool, urgency, and incomplete evacuation. Although overall scores of 36-item Short Form Health Survey (SF-36) for the two groups were not significantly different, patients in the peppermint oil group showed improvements in the SF-36 domains of bodily pain, general health, social functioning, and role limitations due to emotional problems.

A recent 2016 study by Cash et al 41 reported the findings of a 4-week double blinded, placebo controlled randomized controlled trial which tested a novel formulation of peppermint oil designed for sustained release in the small intestine (IBgard®, IM HealthScience, Boca Raton, FL, USA) for its efficacy and tolerability in reducing IBS symptoms in 72 patients with mixed IBS (IBS-M) or IBS with diarrhea (IBS-D) by Rome III criteria. The specialized enteric-coating utilized in their trial consisted of a solid-state matrix that was triple-coated and designed to deliver peppermint oil with sustained release to the small intestine with fewer potential adverse effects. At trial completion, there was a 40% reduction in the total IBS symptom score in the peppermint oil group compared to baseline vs. 24.3% with placebo 41. Moreover, there was an increased improvement in both multiple and individual gastrointestinal symptoms, as well as in severe or unbearable symptoms compared to the placebo.

Similarly, some meta-analyses have shown peppermint oil to be effective in IBS, the number needed to treat ranged between 2 and 3 42. In most recent meta-analysis of 12 randomized controlled trials with 835 patients with IBS, the risk ratio (RR) for the effect of peppermint oil (n = 253) versus placebo (n = 254) on global symptoms was 2.39 43. Overall, there were no differences in the reported adverse effects, peppermint oil (9.3%) versus placebo (6.1%). The number needed to treat with peppermint oil was three for global symptoms and four for abdominal pain.

Table 2. Summary of clinical trials of peppermint oil

SubjectDesignCountyComparisonNumberOutcomeRef.Jadad score
IBS based on symptomsSingle center, randomized, double-blind, placebo-controlledTaiwanPeppermint oil 137 mg three times a day or four times a day, before meal, 4 weeks vs. placebo25:49:00Symptom improvements after peppermint oil therapy were significantly better than after placebo.Liu et al. 444
IBS by Rome IISingle center, randomized, double-blind, placebo-controlledItalyPeppermint oil 450 mg two times a day, before meal, 4 weeks vs. placebo28:29:00A 4-week treatment with peppermint oil is more effective than placebo in reducing abdominal symptoms related to IBS.Cappello et al. 394
IBS by Rome IISingle center, randomized, double-blind, placebo-controlledIranPeppermint oil 187 mg three times a day, before meal, 8 weeks vs. placebo33:27:00Severity of abdominal pain and discomfort were reduced significantly in the peppermint oil group.
Peppermint oil significantly improved the quality of life.
Merat et al. 405
IBS by Rome IIIMulticenter, randomized, double-blind, placebo-controlledUSAPeppermint oil 180 mg three times a day, 4 weeks vs. placebo35:37:00Patients treated with peppermint oil experienced greater improvement in multiple individual gastrointestinal symptoms as well as in severe or unbearable symptoms, compared to placebo.Cash et al. 415
Childhood IBS by Manning or Rome IIMulticenter, randomized, double-blind, placebo-controlledUSAPeppermint oil 374 mg or 187 mg three times a day, 2 weeks
21:21:00After 2 weeks, improvements in the change of symptom scale were reported in 71% of the patients receiving peppermint oil compared with 43% receiving placebo with statistical significance.Kline et al. 453
Functional dyspepsia based on symptomsSingle center, randomized, double-blind, placebo-controlledGermanyPeppermint oil 90 mg and caraway oil 50 mg two times a day, 4 weeks vs. placebo48:48:00For the major symptoms (intensity of pain, sensation of pressure, heaviness and fullness, and global improvement), the superiority of combination therapy of peppermint oil and caraway oil over placebo was statistically significant.May et al. 465
Functional dyspepsia by Rome IIIMulticenter, randomized, double-blind, placebo-controlledGermanyPeppermint oil 90 mg and caraway oil 50 mg two times a day, 4 weeks vs. placebo58:56:00Compared to placebo, 4-week treatment with peppermint oil and caraway oil therapy significantly reduced symptoms of epigastric pain and postprandial distress and improved the participants’ quality of life.Rich et al. 475

Footnote: The Jadad score 48 is often used to assess the methodological quality of controlled trials. Studies are scored according to the presence of three key methodological features of clinical trials, specifically randomization, masking, and accountability of all patients, including withdrawals. One point is added for a “yes” answer to each of the first five items, and one point is subtracted for a “yes” answer to either of the last two items, for an overall score from 0–5. Its short length and ease of use remain as attractions; the 3 feature brevity gives the least responder burden 49.

Reduction of colonic spasm during gastrointestinal procedures

As a consequence of peppermint oil’s relaxing properties on smooth muscle, peppermint oil given via enema has been examined in two trials as a means to reduce symptoms of gastrointestinal spasm during administration of barium enema and possibly during colonoscopy 50, 51. In a randomized controlled trial of 383 patients undergoing barium enemas, 37 to 41 percent of those who received peppermint oil experienced a non-spasm examination, compared with 13.4 percent of those who received placebo 50. In an randomized controlled trial of 141 patients undergoing barium enemas, no residual spasm was evident in 60 percent of the treated group, compared with 35 percent of the control group 51.

Non-ulcer dyspepsia (functional dyspepsia)

A combination of enteric-coated peppermint oil and caraway oil has been shown in several clinical trials to reduce symptoms of non-ulcer dyspepsia (e.g., fullness, bloating, gastrointestinal spasm), but the specific preparation used in these trials is not available in the U.S. 52, 53. A meta-analysis of several trials of a preparation containing peppermint and caraway oils plus other herbal extracts (Iberogast) found it to be effective in the treatment of functional dyspepsia 54. This benefit may be the result of the preparation’s relaxing effect on the lower esophageal sphincter, with concomitant equalization of pressure between stomach and esophagus and reduced sensation of bloating and abdominal pressure. However, this effect theoretically could result in reflux symptoms in patients predisposed to gastroesophageal reflux. Because multiple herbs were used in these trials, it is difficult to draw definitive conclusions about the specific effects of peppermint in this condition.

Recently, a randomized placebo-controlled trial with 114 outpatients with chronic or recurrent functional dyspepsia demonstrated that a fixed peppermint and caraway- oil combination (Menthacarin) treatment is effective for the relief of functional dyspepsia symptoms and improvement of disease-specific quality of life 47. After 4 weeks of treatment, pain and discomfort scores improved by 7.6 ± 4.8 and 3.6 ± 2.5 points for Menthacarin and by 3.4 ± 4.3 and 1.3 ± 2.1 points for placebo, respectively 47.

Tension headache

Two trials have shown that topical application of peppermint oil is effective in reducing symptoms of tension headache 55, 56. In one randomized controlled trial, 32 patients were tested using a variety of topical herbal preparations 55. Compared with persons who received placebo, there was a significant analgesic effect in patients who applied a peppermint and ethanol preparation. A second randomized controlled trial that compared the effectiveness of topical peppermint oil and acetaminophen on 164 headaches in 41 patients found that a 10% peppermint oil preparation significantly reduced headache intensity after 15 minutes 56. There was no significant difference in effectiveness between peppermint oil and acetaminophen, and no adverse effects were reported.

Peppermint oil dosage

The dosage of peppermint oil for the treatment of gastrointestinal diseases usually ranges from 0.2 to 0.4 ml, three times a day in enteric-coated capsules 57. The dosage of peppermint oil used in the single clinical trial in children was 0.1 mL three times daily for children weighing less than 45 kg (99 lb, 3 oz) 58. The oral dosage of peppermint oil range studied in most IBS trials was 187 to 500 mg (0.2–0.4 ml) administered two or three times daily for 2 to 8 weeks 40. To secure the availability of unmetabolized peppermint oil at the target organ, a lower digestive tract in IBS, enteric-coated formation such as Colpermin® and Mintoil® (Cadigroup, Rome, Italy) capsules have been developed and have been widely used in clinical trials or real-world practice 39. Each capsule of Colpermin® and Mintoil® contains 187 mg and 225 mg peppermint oil, respectively 57. These formulated capsules are usually administered 30 to 60 minutes before meals in order to guarantee low gastric pH which prevents untimely capsule dissolution with premature release of peppermint oil into the stomach 39.

In functional dyspepsia, most trials used a dose of 90 mg of peppermint oil in combination with 50 mg of caraway oil in a specific standardized preparation that is not currently available in the United States 47.

Peppermint oil toxicity and safety

Peppermint oil has been used safely for various conditions in short-term clinical trials. In a randomized controlled trial with 90 patients with IBS, the most common adverse events of peppermint oil treatment group were heartburn, headache, and dizziness. However, these were not significantly different in the two groups 40. However, peppermint oil is relatively contraindicated in patients with hiatal hernia or significant GERD, because its effects on the lower esophageal sphincter can lead to exacerbation of symptoms 3. Especially, when non-coated peppermint oil is taken orally, it can cause heartburn, nausea, and vomiting. The effective delivery method to the target organ by enteric coating is believed to prevent or reduce these upper gastrointestinal symptoms as well as improve peppermint oil efficacy 3. Even in the enteric coated formulation, heartburn could develop because of the premature rupture of capsules containing peppermint oil 59. High concentrations of peppermint oil have been reported to cause anal burning 60. Other minor adverse effects of peppermint oil reported in clinical trials include allergic reactions and blurred vision. Because peppermint oil may inhibit the cytochrome P450 system, it theoretically could lead to increased serum levels of drugs such as amitriptyline, haloperidol, and cyclosporine which are metabolized by this enzyme 61. However, this interaction has not been proven in humans.

Toxicology studies of peppermint oil and its components have been performed in animals. Histopathological changes in the white matter of the cerebellum were seen in rats (n = 20) given peppermint oil at doses of 40 and 100 mg/kg orally for 28 days, but no adverse effects were observed at 10 mg/kg 62. No adverse effects were observed at 10 mg/kg. In a comparable 90 day rat study (n = 28), cyst-like spaces in the white matter of the cerebellum and hyaline droplets in the proximal tubules of the kidneys were observed in the highest dose group only 63. Interestingly, the extension of the cyst-like spaces was not aggravated with prolonged dosing in this study. Menthol administered to rats by gavage at 200, 400 and 800 mg/kg for 28 days significantly increased absolute and relative liver weights and the vacuolization of hepatocytes at all doses, although no sign of encephalopathy was observed 64. At 80 and 160 mg/kg, pulegone administered for 28 days induced atonia, decreased blood creatinine levels, lowered body weight and caused histopathological changes in the liver and white matter of the cerebellum 64. No adverse effects were observed with 20 mg/kg pulegone. Menthone given orally to rats (n = 20) at 200, 400 and 800 mg/kg for 28 days decreased creatinine and increased alkaline phosphatase in a dose-dependent manner, increased bilirubin and liver and spleen weights, and also caused histopathological changes in the white matter of the cerebellum in the two highest dose groups 65. The accumulation of protein droplets containing α2μ-globulin in proximal tubular epithelial cells of rats (n = 10/group) was observed after the administration of either 500–1000 mg/kg 1,8-cineole or 800–1600 mg/kg limonene for 28 days, however, no histopathological changes were observed in the brain 66.

  • Although peppermint is commonly available as an herbal supplement, there are no established, consistent manufacturing standards for it, and some peppermint products may be contaminated with toxic metals or other substituted compounds.
  • Peppermint oil appears to be safe when taken orally (by mouth) in the doses commonly used. Excessive doses of peppermint oil can be toxic.
  • Short-term and sub-chronic peppermint oil oral studies reported cystlike lesions in the cerebellum in rats that were given doses of Peppermint Oil containing pulegone, pulegone alone, or large amounts (>200 mg/kg/day) of menthone. Pulegone is also a recognized hepatotoxin 67.
  • Possible side effects of peppermint oil include allergic reactions and heartburn. Capsules containing peppermint oil are often enteric-coated to reduce the likelihood of heartburn. If enteric-coated peppermint oil capsules are taken at the same time as antacids, the coating can break down too quickly.
  • Like other essential oils, peppermint oil is highly concentrated. When the undiluted essential oil is used for health purposes, only a few drops are used.
  • Side effects of applying peppermint oil to the skin can include skin rashes and irritation. Repeated intradermal dosing with Peppermint Oil produced moderate and severe reactions in rabbits, although Peppermint Oil did not appear to be phototoxic. Peppermint oil should not be applied to the face or chest of infants or young children because serious side effects may occur if they inhale the menthol in the oil.
  • A study on diet and the development of gastroesophageal reflux disease (GERD) 68 found that frequent consumption of peppermint tea was a risk factor for the development of gastroesophageal reflux disease (GERD). Gastroesophageal reflux disease (GERD) is a chronic gastrointestinal disease that significantly reduces quality of life and, in some patients, leads to serious complications, such as oesophageal stricture, gastrointestinal bleeding, or Barrett’s oesophagus. According to various sources, the typical symptoms of this disease (heartburn, discomfort in the upper abdomen, acid eructation) are experienced daily by 4–10%, and weekly by 10–30% of the adult population in Western countries 69. Literature sources suggest that peppermint decreases lower esophageal sphincter (LES) tension; moreover, peppermint oil (studied in animal models) relaxes the smooth muscles of the alimentary tract 70. Oliveria et al. 71 found that 8% of heartburn patients reported complaints after consuming peppermint. In contrast, Terry et al. 72 and Bulat et al. 73 did not observe any effect of consuming products and beverages with peppermint on reflux episodes. This issue requires further research.
  • The long-term safety of consuming large amounts of peppermint leaf is currently unknown.

A review on the use of peppermint oil, leaf extract, leaf and leaf water in cosmetic formulations by Nair 74 concluded that each are considered safe, although the concentration of pulegone in products containing these ingredients should be limited to 1%. Although the toxicity of menthol is considered to be low, it has the ability to enhance the penetration and absorption of other agents contained in some formulations, thereby increasing the effective dose of these agents at the indicated intake. A few case study reports have described contact sensitivities to peppermint oil and its components in topical and oral preparations 75, 76, but a patch test study of 4000 patients by Kanerva et al. 77 found that menthol and peppermint oil provoked neither allergic nor irritant reactions.

Akdogan et al. 78 reported increased follicle stimulating hormone (FSH) and luteinizing hormone  (LH) levels and decreased testosterone levels in rats given 20 g/L peppermint tea in place of their drinking water. As opposed to spearmint tea, the only effect of peppermint on testicular tissue was segmental maturation arrest in the semniferous tubules. There are no chronic toxicity studies of peppermint in humans, although the German Commission E 79 reports that the use of peppermint oil is contraindicated in patients with bile duct, gallbladder and liver disorders. Caution is also recommended for the use of peppermint oil capsules in patients with GI reflux, hiatal hernia or kidney stones.

Peppermint oil summary

  • Peppermint oil has been studied most extensively for IBS. Results from several studies indicate that peppermint oil in enteric-coated capsules may improve IBS symptoms in adults.
  • Peppermint oil was shown to be a safe and effective therapy for pain and global symptoms in adults with IBS.
  • One small study suggests that peppermint oil in enteric-coated capsules may reduce abdominal pain in some children.
  • A few studies have indicated that specific products containing peppermint oil plus caraway oil and specific combination products that include peppermint leaves may help relieve indigestion. But there isn’t any evidence showing that taking peppermint oil alone can help. In fact, peppermint oil taken alone may worsen indigestion in some people and cause unwanted side effects.
  • A small amount of research suggests that peppermint oil might be helpful to reduce spasms during certain procedures, such as endoscopy or barium enema examination.
  • Peppermint oil has been used topically for tension headaches and a limited amount of evidence suggests that it might be helpful for this purpose.
  • Peppermint oil in a gel, water, or cream applied topically to the nipple area of breastfeeding women might be helpful for reducing pain and cracked skin. Menthol, which is in peppermint oil, should not be inhaled by or applied to the face of an infant or small child because it may negatively affect their breathing. Peppermint oil should therefore be used only after breastfeeding and then wiped off before the next breastfeeding session.
  • There’s not enough evidence to allow any conclusions to be reached about whether peppermint oil is helpful for nausea, the common cold, or other conditions.
  • There’s not enough evidence to show whether peppermint leaf is helpful for other conditions.
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