This results from the action of extreme cold (below 0 °C) on the skin. VASOCONSTRICTION results in a reduced blood – and hence, 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), who 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, such as the cheeks or nose, 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, then in a matter of months the dead tissue peels oﬀ. In the most severe cases of all, 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.
Prevention 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.
Treatment 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. In essence this consists of warming the aﬀected part, preferably in warm water, against a warm part of the body or warm air. Rewarming should be done for spells of 20 minutes at a time. 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.