Frostbite, or freezing of body tissues, is one of the worst dangers of winter hiking, camping, or skiing. To survive, learn to prevent it and treat it.
The cold isn't the only factor in frostbite. Windchill, moisture, skin exposure, body type, dehydration, previous frostbite, and use of alcohol or caffeine can all contribute to frostbite. Another factor is your body's response to cold. When you start getting cold, blood flow increases to your core to prevent hypothermia, leaving less blood to your extremities. If hypothermia is a possibility, treat that first.
Frostbite falls into two categories, superficial and deep. Superficial frostbite causes you to feel burning and tingling when surface tissue starts freezing. Sometimes called frostnip, only the top layers of skin freezes and it's usually reversible. Your skin will look waxy and pale, and become numb, but deeper tissues stay unfrozen. Deep frostbite can affect your muscles and bones; the affected area will feel hard and look dead and blackened.
The first parts of your body endangered by frostbite are fingers, toes, ears, and nose. Wear insulated gloves, warm insulated boots, a warm hat that covers your ears, and something to cover your nose. Consider wearing a pair of lightweight gloves inside your regular gloves, and look for wool socks that will stay warm when wet. Make sure the socks, gloves, and any other clothes aren't too tight. Constricting clothes contribute to frostbite. If you feel numbness or tingling in these body parts, head for shelter and warmth.
If you're far from medical help, start with first aid. Gently but quickly warm the affected area, holding it against someone else's warm body if necessary. Do not rub the frostbitten area; that can cause cell damage. If possible, put the affected part into warm, not hot, water. Wrap the affected area with sterile gauze from a first aid kit. Put cotton between fingers and toes so they don't rub against each other. Put dry warmed feet into booties to keep them warm. Give the injured person ibuprofen and warm fluids. Finally, if you're not absolutely sure that you can keep the frost-bitten area from freezing again, don't try to warm it. Keep it frozen and get to medical assistance as quickly as possible.
Untreated, frostbitten fingers, toes, hands and feet may become gangrenous and need amputation. Don't take frostbite lightly if you want to survive.
(Sources: http://www.webmd.com/a-to-z-guides/frostbite , http://www.mayoclinic.com/health/first-aid-frostbite/FA00023 , http://www.mayoclinic.com/health/fitness/HQ01681 , http://princeton.edu/~oa/safety/hypocold.shtml )
