Herbs & Supplements:
Peppermint
Mentha piperita

Principal Proposed Uses
  • Oral: Irritable Bowel Syndrome, Oral: Other Forms of Intestinal Spasm, Oral: Dyspepsia
Other Proposed Uses
  • Inhaled (aromatherapy): Respiratory Congestion, Nausea, Topical: Tension Headaches, Oral: Gallstones

Peppermint is a relative of numerous wild mint plants, deliberately bred in the late 1600s in England to become the delightful tasting plant so well known today. It is widely used as a beverage tea and as a flavoring or scent in a wide variety of products.

Peppermint tea also has a long history of medicinal use, primarily as a digestive aid and for the symptomatic treatment of cough, colds, and fever. Peppermint oil is used for chest congestion (Vicks VapoRub), as a local anesthetic (Solarcaine, Ben-Gay), and most recently in the treatment of irritable bowel disease, also known as spastic colon.

What Is Peppermint Used for Today?

Germany's Commission E authorizes the use of oral peppermint oil for treating colicky pain in the digestive tract. Some preliminary evidence suggests that peppermint oil may indeed be effective for this purpose.

The active ingredient of peppermint oil for this purpose is thought to be menthol. This substance relaxes the muscles of the small intestine in dilutions as low as 1:20,000, and has been found to counter the effect of drugs that cause intestinal spasm.^3,4,5 Peppermint oil may also be helpful for dyspepsia (minor indigestion).

Oral peppermint oil has also shown some promise for helping to dissolve gallstones, ¹ but it is far from a proven treatment for this condition.

Peppermint oil is also used in another way: as aromatherapy. This means that it is inhaled, often by adding it to a humidifier. The Commission E has authorized inhaled peppermint oil for relief of mucus congestion of the lungs and sinuses; however, there is only weak supporting evidence for this use. ^{21, 22} Even weaker evidence hints that inhaled peppermint oil might relieve post-surgical nausea. ²

Similarly weak evidence hints that peppermint oil, applied to the forehead, might relieve tension headaches. ^{23, 24}

What Is the Scientific Evidence for Peppermint?

Irritable Bowel Syndrome

The scientific record for peppermint oil in treating irritable bowel syndrome is incomplete. While the preponderance of the evidence suggests that it works, most studies were relatively poorly designed. ²⁵

Four preliminary, double-blind studies, involving a total of about 240 individuals with irritable bowel syndrome, found that peppermint can provide significant relief from crampy abdominal pain.^6–10 In the largest of these, 110 individuals with irritable bowel syndrome were given either enteric-coated peppermint oil (187 mg) or placebo 3 to 4 times daily, 15 to 30 minutes before meals, for 4 weeks.⁸ The results in the 101 individuals who completed the trial showed significant improvements in abdominal pain and bloating, stool frequency, and flatulence. However, other studies, involving more than 90 people, have found no significant improvement in symptoms.^11,12,13

The most probable reason for these contradictory results is that the placebo effect is fairly strong in irritable bowel syndrome; this makes it easy for small studies to miss benefits caused by the actual effects of any treatment.

Other Forms of Intestinal Spasm

A barium enema involves introducing a solution containing the metal barium into the lower intestines. It commonly causes intestinal pain and spasm. A double-blind study of 141 individuals found that adding peppermint oil to the barium reduced the amount of spasming that occurred.¹⁴

Dyspepsia (Minor Indigestion)

Peppermint oil is often used in combination with other essential oils to treat minor indigestion.

A double-blind placebo-controlled study including 39 individuals found that an enteric-coated peppermint-caraway oil combination taken 3 times daily for 4 weeks significantly reduced dyspepsia pain as compared to placebo.¹⁵ Of the treatment group, 63.2% was pain free after 4 weeks, compared to 25% of the placebo group.

Results from a double-blind comparative study including 118 individuals suggest that the combination of peppermint and caraway oil is comparably effective to the no-longer-available drug cisapride.¹⁶ After 4 weeks, the herbal combination reduced dyspepsia pain by 69.7%, whereas the conventional treatment reduced pain by 70.2%.

A preparation of peppermint, caraway, fennel, and wormwood oils was compared to metoclopramide in another double-blind study enrolling 60 individuals.¹⁷ After 7 days, 43.3% of the treatment group was pain free compared to 13.3% of the metoclopramide group.

Dosage

The proper dosage of peppermint oil when treating irritable bowel syndrome is 0.2 to 0.4 ml 3 times a day of an enteric-coated capsule. The capsule has to be enteric-coated to prevent stomach distress.

Safety Issues

At the normal dosage, enteric-coated peppermint oil is believed to be reasonably safe in healthy adults.^18,19

However, if you take too much, peppermint oil can be toxic, causing kidney failure and even death. Excessive intake of peppermint oil can also cause nausea, loss of appetite, heart problems, loss of balance, and other nervous system problems.

Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established. In particular, peppermint can cause jaundice in newborn babies, so don't try to use it for colic.

Use of peppermint oil may increase levels of the drug cyclosporine in the body. ²⁶ If you are taking cyclosporine, and wish to take peppermint oil, notify your physician in advance, so that your blood levels of cyclosporine can be monitored and your dose adjusted if necessary.

Conversely, if you are already taking both peppermint oil and cyclosporine, do not stop taking the peppermint without informing your physician. When you stop peppermint, you cyclosporine levels may fall.

Interactions You Should Know About

If you are taking cyclosporine, do not use peppermint oil (or stop using it) except in consulation with your physician.

Last reviewed June 2002 by Medical Review Board

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