Ice promotes healing by constricting the blood arteries that bring these toxic chemicals (cytokines) to the injury, so slowing the inflammatory process. It also reduces pain by controlling the temperature of the injured area and by blocking nerve signals from reaching it. Ice is particularly useful for treating injuries such as strains or sprains. It can also be used to reduce the pain of a tooth extraction or other surgery. The cold temperatures of ice blocks slow down the body's natural reaction to injury, allowing the skin to heal faster. When applied directly to an injury, ice limits the flow of blood to the area, reducing the number of cells that are damaged by lack of oxygen. This helps prevent scarring and keeps wounds clean. Ice may also relieve pain by causing muscles to relax and by reducing the activity of certain nerves near the injury site. People sometimes ask why ice was not used more often during ancient times when there were no antibiotics to treat infections. The answer is that ice applications did exist but they were not used regularly. They were usually only used when someone had a knife taken out of their hand or a snake bit them. There are even stories about rulers using ice on enemies who threatened them! Today, ice is still used to help injuries heal faster and prevent scars.