Field treatment of frostbite is possible but with exception to very minor cases, medical treatment should always be sought out. The most important step in treating frostbite is to make sure you will not refreeze the injured area. If you are in an emergency situation and come to a shelter, you will do far worse injury to yourself or an injured friend treating your frostbite and then moving on to the trailhead, only to get frostbite in the same areas when you start to move again. When treating yourself or someone else for frostbite you should also check for signs of hypothermia, as the two medical conditions typically go hand in hand. Never attempt to field treat third degree frostbite. It is a life threatening medical condition that needs to be treated by a trained professional.
The most logical step for treatment is to get out of the cold and out of the wind. Warm the frostbitten areas slowly, and start at the outer extremities and work your way in (toes to feet, fingers to hands, nose to cheeks) using warm breath or by tucking the hands or feet inside warm clothing by bare warm flesh (armpits and groin areas work best).
For broader areas of frostbite (when more than a toe or earlobe is involved) keep the frostbitten area elevated. Wrapping the injured area in warmed blankets. If possible immerse in warm water (104 to 108 degrees - similar in temperature to what you would bathe a new born baby in) for 15 to 30 minutes. Please note that immersion can become quite painful as the flesh begins to thaw out. You should never rub or massage the frozen areas, doing so only rubs the ice crystals around on the delicate cell walls and causes further injury and damage.
Unless your life absolutely depends on it, never walk on frostbitten feet. If blisters form during rewarming do not break or drain them. The skin as it thaws out may turn red, could tingle, burn or be very painful. If you experience pain during the rewarming process, get blisters, or have tissue damage you should seek medical attention immediately. Never rewarm a frostbitten area on your own if you can get conventional medical help and advice in a timely fashion.
Prevention of frostbite is actually very simple and for the most part is based on common sense.
Understand the prevailing weather conditions. Remember not only air temperature but wind speed effects how quickly frostbite can occur. Be prepared for worse than what the weatherman calls for.
Wear layers of clothing and protect exposed skin from the elements. A number of very good man made insulators are available on the market from a number of manufacturers. Wool is the best natural insulator. Cotton should be avoided if you are in conditions where you might get wet.
Wool socks, VVS, with liner socks made of Wick Dry or Cool Max, with good boots that are waterproofed help keep your feet warm. In more extreme conditions consider wearing mountaineering boots.
Wear a hat that will cover your ears. If you are in extreme cold or windy conditions, a ski mask or facemask is helpful. In the most severe conditions, total coverage of your face, including ski goggles may be required so that not the tiniest bit of skin is exposed on the face or head.
Don't drink alcohol, consume caffeinated drinks or smoke when out in the extreme cold. All of these activities encourage hypothermia and frostbite.
Frostbite is a very preventable and treatable outdoor-related injury. A little careful preparation and understanding is all it takes to protect you from serious injuries while enjoying the outdoors. Jack Frost may nip at your nose, but if it's properly covered you'll never know.