Cryotherapy is the medical term that describes the application of ice compresses to reduce the temperature of tissues directly on or below the skin surface. Cryotherapy works on the surface of the skin, cooling and constricting blood vessels, "anesthetizing" painful areas, and assisting in the relaxation of muscle spasms. Cold temperatures reduce nerve transmission of painful symptoms and provide temporary relief. Cooling affected tissues has proven effective in reducing and preventing post-traumatic swelling. Local cooling should be applied several times a day during the initial stages of an injury.
