(MEN-thol) A substance that comes from mint oils or is made in the laboratory. It is used to relieve itching and to treat problems in the upper respiratory tract. Menthol causes a cooling sensation when eaten or put on the skin and it acts as a mild pain killer. It is found in nasal sprays, cough drops, inhalers, creams, and lotions. It is also used as a flavor in many food and oral hygiene products.