True frostbite causes permanent damage to the frozen tissue. Blisters usually form, along with a thick black scar. Gangrene can occur with loss of a toe or finger in severe cases. Superficial frostbite will occur if the exposed area is not rewarmed after frostnip occurs. In such cases, the skin becomes white and cold, but the tissue beneath is still soft.
Treatment involves rapidly rewarming the area if there is no danger of refreezing.
The affected area should be submerged in a warm water bath for 20-30 minutes or until color returns. A bath that is too hot or the rubbing of ice or snow on the area can cause permanent damage. A heating pad or other heating apparatus should not be used because the temperature cannot be controlled and rewarming the part must be done evenly. When rewarmed, the frozen area becomes red and swollen, and a burning sensation is felt. Blisters appear within hours or days and the fluid in the blisters is absorbed during the following weeks.