The parts of the body most commonly frostbitten are the ears, tip of the nose, fingers, and toes. Damage is caused both by the formation of ice crystals in tissues and by drastic reduction of blood flow in the frozen areas. Be careful, the numbing effect of cold may allow frostbite to occur without warning. Often when you feel discomfort in an exposed area, frostbite has already occurred. The skin in the frostbitten area is hard, numb, and yellowish-white.
Frostbite can be superficial or deep.
If it is superficial, redness and blisters appear after thawing. If it is deep, swelling appears under the skin after thawing and persists for a day or two, after which gangrene may develop. During healing, a black crust develops over the frostbitten area, but it later peels off. Superficially frostbitten tissue may be thawed immediately by one's own or another person's body heat. However, the frozen tissue should not be exercised or rubbed with snow.