Peppermint was first described in 1753 by Carolus Linnaeus from specimens that had been collected in England; he treated it as a species but it is now universally agreed to be a hybrid.
It is a herbaceous rhizomatous perennial plant growing to 30–90 cm) tall, with smooth stems, square in cross section. The rhizomes are wide-spreading, fleshy, and bare fibrous roots. The leaves are from 4–9 cm long and 1.5–4 cm broad, dark green with reddish veins, and with an acute apex and coarsely toothed margins. The leaves and stems are usually slightly hairy. The flowers are purple, 6–8 mm long, with a four-lobed corolla about 5 mm diameter; they are produced in whorls (verticillasters) around the stem, forming thick, blunt spikes. Flowering is from mid to late summer.

Peppermint oil has a high concentration of natural pesticides, mainly menthone.
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.
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. Peppermint relaxes the gastro-esophageal sphincter.