Cryotherapy is a 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 cooling constricts blood vessels, numbs painful areas, and helps relax muscle spasms. Cold temperatures reduce nerve transmission of painful symptoms and provide temporary relief. Cooling affected tissues is effective in reducing and preventing post-traumatic swelling. Local cooling should be applied several times a day during the initial stages of an injury.