Peppermint is widely used for its antispasmodic, antiseptic, carminative, anesthetic, and choleretic properties. It aids digestion and is held to be helpful for many stomach problems, irritable bowel syndrome, nausea, morning sickness, dysmenorrhea, diarrhea, constipation, and flatulence. In larger doses, it may have an emmenagogic effect. Studies show that peppermint oil acts as a choleretic, stimulating the flow of bile, which improves digestion. Peppermint oil also has antiviral properties, inhibiting many viruses that cause digestive problems.

Menthol, a major constituent of peppermint oil, is well known for its external analgesic counter-irritant effects. It cools as well as numbs the skin, producing effective relief from the itching caused by hives and poison ivy. A combination of peppermint oil's analgesic and antispasmodic properties also make it an effective remedy for headaches. Studies suggest that correct use of the oil can be as effective as taking 1 g of acetaminophen.

Peppermint and menthol appear most frequently in cold medicines, where they are effective as decongestants. The strong antiviral properties of peppermint are most concentrated in the tea form, and drinking it will restrict the growth of many cold and flu viruses. It is also very effective for a dry cough, because it calms the throat muscles, and as an expectorant, because menthol thins the mucus.

Square stems grow up to two feet tall. Flowers are tiny, purple, in whorls and terminal spikes, with four stamens. Leaves are opposite, simple, toothed, and very fragrant. It blooms from July through August. Peppermint is native to Europe and Asia; some types are indigenous to South Africa, South America, and Australia. It is naturalized in North America and cultivated primarily in Oregon, Washington, and Wisconsin.

• Flower
• Leaves
• Oil

The herb consists of the leaves and flowering tops of Mentha piperita (family Lamiaceae) and is made up of volatile oil (0.5% to 4%) composed of 50% to 78% menthol and 5% to 20% menthol esterfied with various organic acids, such as acetic and bovaleric. Also flavonoids (luteolin, menthoside), phenolic acids, and triterpenes.

Packaged peppermint tea is widely available or may be made from dried fresh peppermint leaves.

Tinctures: Peppermint spirit is an alcoholic solution containing 10% peppermint oil and 1% peppermint leaf extract. To make a tincture, add one part peppermint oil to nine parts pure grain alcohol.

Enteric-coated capsules (0.2 ml of peppermint oil per capsule)

Creams or ointments (should contain 1% to 16% menthol): Mentholatum or Vicks VapoRub

Traditional: antispasmodic, carminative, choleretic, antibacterial, decongestant, external analgesic, antiemetic, aromatic, emmenagogue, antiparasitic, stimulant

Conditions: irritable bowel syndrome, nausea, morning sickness, diarrhea, dysmenorrhea, constipation, flatulence, gallstones, headache, hives, nasal congestion, dry cough

Clinical applications: irritable colon, catarrhs of respiratory tract, inflammation of oral mucosa, myalgic and neuralgic conditions

Peppermint's primary active component is menthol, the focus of most scientific experiments, which have determined it to be effective internally as an antispasmodic, carminative, choleretic, decongestant, and antibacterial, and externally as an analgesic.

Peppermint's carminative properties work by relaxing the esophageal sphincter, allowing gas pressure to escape the stomach. Because of this, peppermint should not be used in cases of gastroesophogeal reflux disease because it may exacerbate the condition. A recent study reported that 89.5% of patients with irritable bowel syndrome showed significant improvement in abdominal symptoms after being treated with enteric-coated peppermint oil capsules. The enteric coating allows the peppermint oil to reach the intestines without being absorbed into the stomach. In the intestines, the oil is believed to inhibit the hypercontractility of intestinal smooth muscle and restore proper muscle tone.

In vitro studies show that peppermint oil can inhibit and destroy influenza A viruses, herpes simplex, mumps virus, Streptococcus pyogenes, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. The menthol and related terpenes found in peppermint oil have been shown by several studies to dissolve gallstones by lowering bile cholesterol levels while raising bile acid and lecithin levels in the gallbladder.

Peppermint works as an external analgesic by blocking muscle contractions caused by serotonin and substance P, but it also stimulates cold receptors on the skin, which may influence the spinal cord's pain transmissions. The oil also relaxes the pericranial muscles and increases blood flow to the capillaries, making it an effective treatment for headaches.

• For digestion and upset stomach, peppermint tea (infusion), 1 to 2 tsp. of dried leaves per 8 oz. of water, 3 to 4 cups daily between meals; peppermint glycente for children, 1 to 2 ml daily
• For gallstones and irritable bowel syndrome, 1 to 2 enteric-coated capsules tid between meals
• As an external analgesic, menthol in a cream or ointment form no more than tid to qid
• For upset stomach or vomiting, 3 to 6 g of leaf, or 5 to 15 drops of tincture
• For tension headaches, tincture of peppermint oil. Apply light coating to entire forehead with fingertips or small sponge. If there is occipital pain, apply to back of neck as well. Allow to evaporate.

When taken as a tea, peppermint is usually considered safe, although hypersensitivity reactions have been reported. Rare negative reactions to enteric-coated peppermint oil capsules may include skin rash, heartburn, bradycardia (slowed heartbeat), and muscle tremors. Menthol or peppermint oil applied topically could cause contact dermatitis or rash. Peppermint oil should be diluted and taken in small amounts, as excessive ingestion could cause interstitial nephritis and acute renal failure. An estimated fatal dose of menthol is 2 to 9 g if taken internally. There are no known mutagenic or carcinogenic effects.

No contraindications to peppermint as an herb. Peppermint oil is contraindicated by biliary tract obstruction, cholecystitis, and severe liver damage. Infants and small children should not use peppermint tea or oil. Pregnant or nursing mothers should use peppermint tea only in small doses and those with a history of miscarriage should avoid it. Do not mistake oil for tincture preparations.

In a study evaluating potential essential oils as transdermal delivery agents, peppermint oil acted as a penetration enhancer for 5-fluorouracil (5-FU) using excised rat skin (Abdullah et al. 1996). Peppermint oil enhanced the permeation of 5-FU approximately 46-fold. The mechanism for the accelerated percutaneous absorption of 5-FU combined with these essential oils may be due to a combination of partition and diffusion.

On the U.S. FDA's list of herbs, peppermint is generally regarded as safe as a dietary supplement. The German Commission E approves it for internal use as an antispasmodic, carminative, choleretic, and decongestant, and for external use as an analgesic.

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