April 13, 2007 -- Peppermint oil is effective in treating digestive disorders and other conditions including headaches, although high dosages may cause adverse effects, according to the results of a review reported in the April 1 issue of American Family Physician.

"The medicinal use of peppermint and other mint plants probably dates back to the herbal pharmacopoeia of ancient Greece, where peppermint leaf traditionally was used internally as a digestive aid and for management of gallbladder disease; it also was used in inhaled form for upper respiratory symptoms and cough," write Benjamin Kligler, MD, MPH, from the Albert Einstein College of Medicine of Yeshiva University in New York, and Sapna Chaudhary, DO, from the Beth Israel Continuum Center for Health and Healing in New York. "Peppermint oil, which is extracted from the stem, leaves, and flowers of the plant, has become popular as a treatment for a variety of conditions, including irritable bowel syndrome (IBS), headache, and non-ulcer dyspepsia."

Specific applications of note are as follows:

• Peppermint leaf and oil have a long history of use for digestive disorders.
• Enteric-coated peppermint oil is a safe alternative to effectively reduce some IBS symptoms, recent evidence suggests, although some evidence is conflicting (evidence rating, B).
• Peppermint oil combined with caraway oil appears moderately effective in treating nonulcer dyspepsia (evidence rating, B).
• Peppermint oil applied topically may effectively treat tension headache (evidence rating, B).
• Peppermint oil has relaxant effects on smooth muscle. When given via enema, it has been shown to be modestly effective in relieving colonic spasm in patients undergoing barium enemas (evidence rating, B).

Although peppermint oil is well tolerated at the commonly recommended dosage, it may cause significant adverse effects at higher dosages. Common adverse effects include allergic reactions, heartburn, perianal burning, blurred vision, nausea, and vomiting. Interstitial nephritis and acute renal failure are rare.

Because peppermint oil may inhibit the cytochrome P450 1A2 system, it may interact with drugs metabolized via this system.

Peppermint oil is contraindicated in patients with hiatal hernia, severe gastroesophageal reflux, and gallbladder disorders and should be used with caution in pregnant and lactating women.

The recommended dosage is 0.2 to 0.4 mL of peppermint oil 3 times daily in enteric-coated capsules for adults, and 0.1 to 0.2 mL of peppermint oil 3 times daily for children older than 8 years.

Cost is approximately $24 to $32 for a 1-month supply.

"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," the authors conclude. "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."

The authors have disclosed no relevant financial relationships.

Am Fam Physician. 2007;75:1027-1030.

Clinical Context

Study Highlights

• Peppermint oil appears to be mildly effective in reducing symptoms of IBS, particularly flatulence, abdominal pain, and distension, in adults. However, there has been significant heterogeneity among research into this subject.
• A study of children between the ages of 8 and 17 years who had IBS found that peppermint oil was more effective than placebo in reducing the severity of abdominal pain.
• 2 trials have demonstrated that treatment with peppermint oil reduced the risk for gastrointestinal spasm during barium enema, with peppermint associated with up to a 3-fold increase vs placebo in the rate of having a procedure free of spasm.
• The combination of 90 mg of peppermint oil plus 50 mg of caraway oil has been demonstrated to reduce symptoms of nonulcer dyspepsia, including fullness, bloating, and spasm. This combination should be used cautiously for patients with dyspepsia, as peppermint oil may promote gastroesophageal reflux.
• 2 studies have delineated the efficacy of topical peppermint oil in tension headache. In 1 study, a combination of peppermint and ethanol was superior to placebo in terms of analgesia. Another trial demonstrated that topical peppermint oil was similar to acetaminophen in terms of treatment efficacy.
• The therapeutic dosage in most trials of peppermint oil and IBS was 0.2 to 0.4 mL taken 3 times daily in enteric-coated capsules. The 1 trial examining its use for childhood IBS used a dosage of 0.1 mL of peppermint oil 3 times daily for children weighing less than 45 kg.
• Peppermint oil can be toxic in overdose, leading to interstitial nephritis and acute renal failure. Because it may promote gallstone formation, it should not be used in patients with cholelithiasis or cholecystitis. Peppermint oil also may trigger menstruation and should not be used during pregnancy.
• The most common adverse events associated with peppermint oil include allergic reactions, heartburn, perianal burning, blurred vision, nausea, and vomiting. Peppermint oil may inhibit the cytochrome P450 1A2 system.

Pearls for Practice

• Peppermint oil contains menthol, menthone, and cineol and may work by relaxing smooth muscle in the gastrointestinal tract. Peppermint oil also may reduce lower esophageal sphincter pressure and therefore usually is supplied with enteric coating.
• Peppermint oil offers mild efficacy for symptoms of IBS and may improve colonic spasm associated with barium enema. Topical formulations of peppermint oil may improve tension headache.

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