cold pack

 A cold pack is a portable bag filled with a substance like water, a gel, or chemicals, used to cool an area of the body to reduce pain and swelling from injuries such as sprains, strains, and bruises. To use one, wrap it in a towel to protect your skin and apply it for 10–15 minutes at a time, with at least 30–40 minutes between sessions to avoid tissue damage. For instant packs, shake them to activate the cold, and for reusable packs, store them in a freezer.