Cold therapy is used to cause vasoconstriction (the blood vessels constrict or decrease their diameter) to reduce the amount of fluid that leaks out of the capillaries into the tissue spaces (swelling) in response to injury of tissue. Ice or cold is used most frequently in acute injuries, but also an effective pain reliever for even the most chronic pain. Cold therapy may be administered by using a cold pack or an ice massage as seen in the above video.