Materia Medica

Mentha piperita   Lamiaceae (Labiatae).  Peppermint is the common name, pa-ho the Chinese name.

The mints have been a universally loved and widely used flavoring for millennia.  The clear historical of use of Mentha piperita does not become evident until the late seventeenth century.  It is apparently a hybrid derived from the cross of Mentha spicata L. and  M. aquatica L.  By 1721 it had become an official plant of the materia medica in the London Pharmacopoeia. 

Peppermint is a universally loved and widely used flavoring in everything from candy to toothpaste to liquor and medicine.  Nearly a million cups of peppermint tea are consumed daily, making it the third most popular tea flavor in the world, behind black tea and chamomile.

There are more than 25 true species of mint naturalized throughout Europe and North America, with peppermint being a fairly recent arrival.  Peppermint is considered a cross between Mentha spicata and M. aquatica and cannot be grown from seed, but must propagated by cuttings.  Peppermint, in the family Lamiaceae, is a perennial that is native to Europe.  It is from one to three feet high with reddish stems and spreads by runners.  The flowers are pinkish or lilac.

Leaves and essential oil are parts used of the plant.  It is available as bulk herb, tea (popular tea flavoring), hydroalcoholic extract, herb capsules, essential oil, enteric-coated essential oil pills, external analgesics and balms, chest rubs, cough lozenges and inhalants.

Menthol constituents are the primary active component of peppermint. Most studies have been with the essential oil of peppermint or a preparation of these oils.

The antispasmodic qualities of peppermint have been fairly well documented.   There is some evidence that the menthol of peppermint oil inhibits contractions of isolated smooth muscles by the blockage of the influx of calcium into the muscle cells.¹   The treatment of irritable bowel syndrome, spastic colon and other intestinal colic has been the main focus of study, and the results have been favorable even if not totally conclusive.  Enteric coated pills are the recommend means of administration, so that the peppermint oil is released into the intestine and not the stomach.^{2 ,3,4}

Peppermint has been traditionally considered to have carminative effects, generally used as tea or digestive tablet or candy.  The exact mechanism is not known, but it is proposed that one way is the essential oils relax the esophageal sphincter, which then releases the gas. ⁵   Essential oils used directly in the stomach, however, give many people heartburn, especially if hiatus hernia is present.

The menthol and related terpenes including menthone, pinene, borneol, cineol and camphene have shown choleretic effects that stimulate the flow and improve the solubility of the bile.  Studies indicate that these oils appear to help dissolve gallstones.^6,7,8

The external analgesic and counter-irritant effects of the menthol in peppermint are well known.  When applied to the skin menthol stimulates the nerves that perceive cold and depress those for pain.  A feeling of warmth follows the initial cooling effect.  This is useful in the treatment of arthritis, fibromyositis, tendonitis and other inflammatory conditions of the mulculoskelatal system.

Peppermint is a popular remedy for colds and flu, often made into a tea with elder blossom and yarrow.  It has been shown to have some antiviral activity primarily from the polyphenols (which dissolve in tea) and a mild diaphoretic effect.  The oil is used in treatment of colds as components of nasal decongestants, cough and throat lozenges, ointments and inhalants.

It is also a frequent home remedy for nausea, gas, colic and upset stomach.  A warm tea is made from the leaves and several cups can be sipped to obtain relief.⁹  Traditionally it has been recommended that for young children, spearmint (Mentha spicata) be used instead of peppermint.

The essential oil of peppermint is used in massage and body oils as an analgesic for sore muscles and musuloskelatal problems.   The oil is reputed to be stimulating to the brain and used as a cephalic.  Peppermint oil, used as an inhalant for postoperative nausea has shown some promising results and bears further investigation.¹⁰

The most active constituent of peppermint is the essential oil, the plant yielding from 0.1% to 1.5%, but is usually present in the 0.3 to 0.4% range.  Menthol is the main component, but it also contains menthone and mentyl acetate and more than 40 other compounds, most of them being terpenoids.  Small quantities of azulene are also found in peppermint oil, which is known to have anti-inflammatory effects.

Other components of peppermint herb include polyphenols, tannins and flavonoids.

The tea is made as an infusion of 1 or 2 teaspoons of the dried leaves, steeped for ten minutes in a covered container.  Enteric-coated capsules for the treatment of irritable bowl syndrome are 1 or 2 capsules,  (0.2 ml/capsule) three times a day between meals.  This is also the dosage recommended for the treatment of gall stones.¹¹

Brinker in Herb Contraindications and Drug Interactions, advises against use in pregnancy, but his is the only reference found to give this warning in both traditional and currant information.  He also advises against its use with gallstones, although in Europe it is used for gallstones.

Peppermint is contraindicated for hiatus hernia because of its relaxing effect of the esophageal sphincter.¹²

Peppermint tea is considered safe (GRAS), there are, however, individual hypersensitive and allergic reactions.  Adverse reactions to enteric coated oil capsules are rare but can include skin rash, heartburn, bradycardia and muscle spasms, these being mainly attributed to the menthol.   Overdose with peppermint oil or capsules may cause mild respiratory distress, transient excitement and possible convulsions.  Management of these are symptomatic, with charcoal and a cathartic to remove any ingested oil still in the gastrointestinal tract.

Topically applied menthol products can cause contact dermatitis and hypersensitivity reactions, which can be enhanced when used in conjunction with heating pads. Do not use peppermint tea and especially peppermint oil for babies and young children.  The application of menthol containing ointments to the nose of an infant for the treatment of a cold has caused apnea and collapse.  Two grams of menthol taken orally is likely to be fatal for an adult human.