Cold & Hypothermia 101: Frostbite
Frostbite typically occurs in any extremities that are exposed to cold temperatures. As the vessels in the extremity constrict due to the cold, they allow less and less warm blood to the area. There are three levels of frostbite: superficial, partial-thickness and full-thickness.
SUPERFICIAL FROSTBITE (1st degree)
Sometimes called “frost nip,” superficial frostbite may appear as white, waxy, cold, frozen skin. After passively rewarming the affected area using tepid water, the frostbitten area may turn red and peel like a sunburn. Give NSAIDs as needed; do not rub or heat the affected area with hot water.
PARTIAL-THICKNESS FROSTBITE (2nd degree)
Partial-thickness frostbite looks very much like superficial frostbite, but may be numb and feel hard to the touch. It may stay indented after being poked. If any blisters (blebs) appear, avoid popping these. Treat any open blebs as open wounds. Slowly rewarm the injury using lukewarm, tepid water and give NSAIDs as needed for pain management.
FULL-THICKNESS FROSTBITE (3rd degree)
In severe cases of full-thickness frostbite, the tissue may first appear white and frozen solid, almost wood-like, but later die and turn black.
Treat frostbite by soaking the injury in tepid, lukewarm water. Hot water will do damage and rubbing the injury will most likely do internal damage to vessels, muscles and skin. Even when thawed out, these injuries are extremely painful and must be evacuated.
NOTE: Chemical hand-warmers are NOT advised, as these instant hand warmers may actually get so hot as to cause thermal burns.
Source: Wilderness First Aid - A Pocket Field Guide (ISBN 9781304726773)