Liniment is is a liquid preparation for application to the skin or to a mucous membrane to relieve pain and increase blood circulation. Liniments generally contain an active principle, the most widely used of which are camphor, chloroform, methyl salicylate (an analgesic compound related to aspirin), and various soaps, dissolved or suspended in a base, usually alcohol or an oil. Liniments are usually applied to the skin by rubbing. The oils and soaps diminish friction during massage, while the alcoholic liniments cause considerable local irritation with resultant reddening of the skin.
Although liniments may be used for several purposes, including providing a protective coating on the skin or mucous membrane, they are most frequently intended to increase blood circulation to an affected area and to relieve pain. Relief of pain may occur not only at the site of application but also in an internal organ at some distance, probably through a poorly understood but often effective process generally referred to as counter-irritation.