Peppermint is a medicinal and edible herb with the scientific name Mentha piperita. According to The Cook's Thesaurus, extracts are flavoring agents made by dissolving a flavored compound in alcohol. Since peppermint extract is made directly from peppermint leaves, it has many of the same properties and applications as the raw herb. The primary chemical in peppermint extract responsible for its medicinal properties and flavors is menthol, an organic alcohol.
The University of Maryland Medical Center recommends peppermint for indigestion, saying, "peppermint calms the muscles of the stomach and improves the flow of bile, which the body uses to digest fats." It also suggests that peppermint can allow gas to pass through the intestine, which helps to relieve gas cramping, and that sufferers of irritable bowel syndrome may get relief from peppermint extract.
The National Institutes of Health (NIH) notes that there is evidence that peppermint extract oils can be used to relieve headache if applied to the temples. It further states that "menthol ... is sometimes included in inhaled preparations for nasal congestion, including 'rubs' that are applied to the skin and inhaled." Peppermint extract, therefore, may be useful in clearing the sinuses.
Topically, peppermint extract is an analgesic and can relieve skin conditions, according to the University of Maryland Medical Center. It soothes skin irritations from hives, poison ivy and poison oak. Much of this effect is due to the numbing properties of peppermint extract's primary ingredient, menthol.