History: Frostbite is a cold-related injury characterized by freezing of tissue on exposure to extreme cold.  Any part of the body may be affected; but hands, feet, nose and ears are the most vulnerable. Cold exposure leads to ice crystal formation, cellular dehydration, protein denaturation, inhibition of DNA synthesis, abnormal cell wall permeability with resultant osmotic changes, damage to capillaries, and pH changes.  Rewarming causes subsequent cell swelling, erythrocyte and platelet aggregation, endothelial cell damage, thrombosis, tissue edema, increased compartment space pressure, bleb formation, localized ischemia, and tissue death.   If only the skin and underlying tissues are damaged, recovery may be complete. However, if blood vessels are affected, the damage is permanent and gangrene can follow which may require amputation of the affected part.