Menthol is an organic compound naturally occurring in mint plants. It is also synthetically manufactured. Menthol is widely used in a number of products and features certain therapeutic qualities. It was first isolated from peppermint oil in 1771 in the West, but it may have been in use in Japan for much longer.

Most of menthol's uses are related to its stimulation of the skin's cold receptors. This property makes menthol produce a cooling effect when inhaled or applied to the skin. Similarly to the capsaicin chemical found in hot peppers, which stimulates heat receptors, menthol does not actually change the skin's temperature, but merely produces the sensation of temperature change.

Because of its cooling effect, menthol is used in products meant to relieve skin irritation, sore throat, or nasal congestion. It may be used to treat sunburn, fever, or muscle aches as well. In traditional Asian medicine, menthol may be prescribed for nausea, diarrhea, indigestion, headache, cold, or sore throat. When used as a supplement for health reasons, menthol is usually taken in the form of peppermint oil. Products that commonly contain menthol include toothpaste, cough drops, lip balm, mouthwash, gum, and cigarettes.

Practitioners of homeopathic medicine believe that menthol can interfere with the efficacy of homeopathic remedies, and some even go so far as to advise against the use of mint toothpaste. Another common claim against menthol is that menthol cigarettes are more dangerous than regular cigarettes, but this has no scientific basis. The idea may be rooted in the fact that African American smokers have both a higher incidence of cigarette-related cancers and a higher preference for menthol cigarettes than smokers of other backgrounds. However, there is no evidence these two statistics are causally related. All types of cigarettes pose significant health risk.

Menthol has very low toxicity, although menthol poisoning is possible if large quantities are consumed. However, any ill effects from the use of menthol are extremely rare. Many people around the world enjoy the cooling sensation of menthol in gum, candy, lip gloss, and other products.