Active Ingredients for Cold Packs

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Whether because of a headache, sprained ankle or any of a number of painful conditions, many of us have encountered ice packs by now. Ice packs work by constricting the flow of blood to an injury site, thus reducing inflammation and pain, and allowing the site to heal faster. Though they often take the form of a bag of crushed ice or frozen vegetables, manufacturers have taken advantage of modern technology to create commercial ice and cold packs. Most of these varieties use gel, instead of water, in order to prevent leaking.

Cellulose Gum

Cellulose gum is also called carboxyl methyl cellulose (CMC). This ingredient is an FDA-approved "food-grade" substance, often used in the food industry as a thickening agent in products like jelly, according to the University of California, Davis. Since cellulose gum is edible and can maintain low temperatures, the food industry also uses it to keep food cool when there's no refrigerator available.

Poly acrylamites, also known as superabsorbers, are the same super absorbent material used in baby diapers, according to the University of California, Davis. When combined with water, it forms a gel-like substance. Superabsorbers are less expensive than cellulose gum when producing cold packs, yet still work effectively at maintaining cold temperatures.

You may recognize silica gel as the stuff in little paper packages that come with your new sneakers. It's actually a very versatile mineral, since its uses range from keeping sneakers fresh to making glass. In the case of cold packs, crystalline silica gel is combined with water to form a gel. This gel can get as cold as 25° F and stay so for up to two hours, according to "Modern Hydrotherapy for the Massage Therapist" by Marybetts Sinclair.

When ammonium nitrate combines with water, a thermal reaction occurs. Heat is immediately released, and the temperature of the mixture is lowered by several degrees, according to the Chemistry Resource Center. This is what happens with "instant" cold packs once the barrier between the ammonium nitrate and the water is crushed. Instant cold packs are ideal for first aid kits and for athletes to carry in their gym bags just in case an injury occurs.