Frostbite is tissue damage resulting from exposure to subfreezing temperatures. Injury to the skin, muscle, blood vessels,
and nerves is caused by formation of ice crystals in these tissues and by a drastic reduction of blood flow in the frozen areas. Early signs of
frostbite include a general numbness of the
affected area and a skin color change from slightly flushed to white to grayish blue as the injury progresses. In mild frostbite the skin feels hard while the underlying tissue is soft. In moderate frostbite, large blisters form on the skin and underlying tissues. Severe frostbite causes major tissue damage often resulting in gangrene from the loss of blood supply to the area.
The frozen area should be thawed with warm water (about 37.8¡ C /100¡ F) as soon as possible and loosely bandaged until medical care is available. The area should not be massaged since this may cause more tissue damage. For mild cases, full recovery is possible, but the affected area often has persistent numbness, sensitivity to cold, and a tendency to repeated frostbite. More severe cases may require amputation of the affected area.