Peppermint oil has a high concentration of natural pesticides, mainly pulegone (Found mainly in Mentha arvensis var. piperascens Cornmint, Field Mint, Japanese Mint and to a lesser extent-6,530 ppm in Mentha x piperita subsp. nothosubsp. piperita) and menthone.

The chemical composition of the essential oil from peppermint (Mentha x piperita L.) was analyzed by GC/FID and GC-MS. The main constituents were menthol (40.7%) and menthone (23.4%). Further components were (+/-)-menthyl acetate, 1,8-cineole, limonene, beta-pinene and beta-caryophyllene.

Medicinal use

In 2007, Italian investigators reported that 75% of the patients in their study who took peppermint oil capsules for four weeks had a major reduction in irritable bowel syndrome (IBS) symptoms, compared with just 38% of those who took a placebo. A second study in 2010, conducted in Iran, found similar results. 2011 research showed that peppermint acts through a specific anti-pain channel called TRPM8 to reduce pain sensing fibres.The authors feel that this study provides information that is potentially the first step in determining a new type of mainstream clinical treatment for irritable bowel syndrome.

According to the German Commission E monographs, peppermint oil (as well as peppermint leaf) has been used internally as an antispasmodic (upper gastrointestinal tract and bile ducts) and to treat irritable bowel syndrome, catarrh of the respiratory tract, and inflammation of the oral mucosa. Externally, peppermint oil has been used for myalgia and neuralgia. According to Commission E, peppermint oil may also act as a carminative, cholagogue, antibacterial, and secretolytic, and it has a cooling action.

Enteric-coated peppermint oil capsules (Colpermin) has been used as an orally administered antispasmodic premedication in colonoscopy. The capsules were found beneficial in reducing total procedure time, reducing colonic spasm, increasing endoscopist satisfaction and decreasing pain in patients during colonoscopy.

Similarly, some poorly designed earlier trials found that peppermint oil has the ability to reduce colicky abdominal pain due to IBS with an NNT (number needed to treat) around 3.1,but the oil is an irritant to the stomach in the quantity required and therefore needs wrapping for delayed release in the intestine. This could also be achieved by using the whole herb or leaves, rather than the volatile components alone.

Due to the menthol constituent, topical use of peppermint oil around the facial or chest areas of infants and young children, especially around the nose, can induce apnea, laryngeal and bronchial spasm, acute respiratory distress with cyanosis, or respiratory arrest. It is also used in construction and plumbing to test for the tightness of pipes and disclose leaks by its odor.

Peppermint oil may cause or worsen heartburn. Peppermint also contains terpenoids and flavonoids such as eriocitrin, hesperidin and kaempferol 7-O-rutinoside.