Overexposure to temperatures below 32 degrees F can result in frostbite, frozen skin and tissue in areas of cold exposure. Fingers are a common site for frostbite, because blood vessels farthest from the heart constrict in cold weather to conserve blood for major organs. Less oxygen reaches the fingers, so cells in the tissue death begin to die. This can lead to gangrene, the University of Wisconsin Stevens Point says.
Outer Layer of Skin Freezing (Mild Frostbite)
In mild frostbite, just the outer layer of skin freezes. The frostbitten fingers turn white as the fluid in the outer skin layer crystallizes. As the fingers warm up, they redden and may stay red for several hours. The skin on the fingers may be painful, itchy and tingly as it thaws, and may be swollen. Mild frostbite is sometimes called frostnip. Mild frostbitten fingers should be warmed slowly; don't use dry heat. If tissue is warmed in water, use warm, not hot, water. Frostbite in the fingers can be prevented by covering the hands with mittens or gloves, and by removing wet hand coverings promptly and either putting on dry gloves or getting out of the cold when first signs appear. Mittens keep your hands warmer than gloves; wearing gloves under mittens affords even more protection. Mildly frostbitten fingers can usually be treated at home.
Hardening Skin (Advanced Frostbite)
In more advanced frostbite, the skin on fingers turns a grayish white and hardens, feeling wooden and numb. The finger may blister, with clear or milk-colored fluid in the blisters. Blisters should not be punctured. Fingers should not be re-warmed and then refrozen; if you can't get to a place where the fingers can be thoroughly thawed out over 45 minutes or so, don't thaw out until you get to where you can. Frostbitten fingers should not be rubbed, especially with snow. Once fingers are warmed, separate frostbitten fingers from one another by wrapping each in sterile dressings, and don't move the fingers any more than necessary. Smoking and alcohol constrict already damaged blood vessels and further decrease blood flow, and should be avoided. Seek medical attention if color and feeling don't return to the fingers promptly, the University of Maryland suggests, or if fever or other new symptoms develop.
Dead Tissue (Severe Frostbite)
Severe frostbite can result in gangrene, or dead tissue. Severely frostbitten fingers turn black and may become infected. Muscles, tendons, nerves, ligaments and bone can be affected, according to the McKinley Health Center at the University of Illinois. Fingers can be so damaged that they must be amputated, but it may take up to six weeks to see how serious the damage is, the University of Michigan Health System says.