A local frostbite occurs, when a body part is exposed to the cold and the temperature drops so low that water in the tissues starts to freeze. The extent of a frostbite is difficult to estimate before it thaws. Small local and superficial frostbites can be easily treated at home.
In winter in Finland, frostbites are rather common, especially when the temperature drops below -20 degrees of Celsius. The risk of frostbite increases with wet clothes and wind. Also smoking and various illnesses and medications that affect the peripheral circulation may increase the risk of frostbites. Frostbites occur especially in the ears, nose, fingers, toes, and cheeks. When the temperature outside the body drops, circulation of the extremities decreases as the body attempts to maintain the core body temperature.
Superficial frostbite
In superficial frostbites, the skin tingles and may feel numb. Gradually, the skin colour changes, the skin looks waxy and pale and feels hard to touch. As the skin gets increasingly numb, pain stops.
A so-called trench foot (immersion foot) may develop in prolonged exposure to cold and wet conditions, which leads to swelling and redness when the foot is warmed.
Deep frostbite
In deep frostbites, the subcutaneous tissue is also damaged. The skin feels numb and hard. You cannot put weight on the frostbitten limb and may lose grip strength. The skin may turn blue and swollen, and blister. The frozen area of skin may even become gangrenous following a severe cold injury. More severe cold injuries must always be treated in hospital without delay. Most of the tissue damage is caused by infection during thawing.