Not medical advice: While Walgreens does not publish the contents of their Instant Cold Packs, according to US Patent 20020046566 A1 (Instant Cold Pack), a plastic cold pack is comprised of a water bag and a coolant consisting of ammonium, sodium carboxyl methyl cellulose, and sodium chloride.
Walgreens® Instant Cold Packs relieve stiff necks, backaches, headaches, and help lower body temperature in case of fever. It is also useful for sport injuries.
According to ABC Online, researchers at the Australian National University have uncovered the exact way pain relief drugs work on the body, which could lead to truly targeted pain medication. Find out more here.