This results from the action of extreme cold (below 0 °C) on the skin. VASOCONSTRICTION results in reduced blood flow and thus oxygen supply, leading to NECROSIS of the skin and, in severe cases, of the underlying tissues. Chiefly affecting exposed parts of the body, such as the face and the limbs, frostbite occurs especially in people exercising at high altitudes, or in those at risk of peripheral vascular disease, such as diabetics (see DIABETES MELLITUS). Such people should take particular care of their fingers and toes when in cold environments.
In mild cases – the condition sometimes known as frostnip – the skin on exposed parts of the body becomes white and numb with a sudden and complete cessation of cold and discomfort. In more severe cases, blisters develop on the frozen part, and the skin then gradually hardens and turns black until the frozen part, such as a finger, is covered with a black shell of dead tissue. Swelling of the underlying tissue occurs and this is accompanied by throbbing and aching. If, as is often the case, only the skin and the tissues immediately under it are frozen, in a matter of months the dead tissue peels off. In the most severe cases, muscles, bone and tendon are also frozen, and the affected part becomes cold, swollen, mottled and blue or grey. There may be no blistering in these severe cases. At first there is no pain, but in time shooting and throbbing pains usually develop.
This consists of wearing the right clothing and never venturing on even quite short expeditions in cold weather, particularly on mountains, without taking expert advice as to what should be worn.
Frostnip is the only form of frostbite that should be treated on the spot. As it usually occurs on exposed parts, such as the face, each member of the party should be on the lookout for it in another. The moment that whitening of the skin is seen, the individual should seek shelter and warm the affected part by covering it with his or her warm hand or a glove until the normal colour and consistency of the affected part are restored. In more severe cases, treatment should only be given in hospital or in a well-equipped camp. Essentially, this consists of warming the affected part – preferably in warm water, against a warm part of the body, or with warm air. Rewarming should be done for spells of 20 minutes at a time, and the affected part should never be placed near an open fire. Generalised warming of the whole body may also be necessary, using hot drinks and putting the victim in a sleeping bag.