When they’re unprepared and unprotected, humans are easy targets for winter weather. Hypothermia, frostbite, and a variety of other injuries related to cold temperatures are all part of the mix.
Hypothermia is an abnormally low core body temperature (95 degrees F or lower) that happens when the body is exposed to cold and loses heat faster than it can make heat. Wet clothing, wind, and cold temperatures (generally lower than 40 degrees F) play a key role in lowering skin temperatures and eventually lower core body temperature. Other factors, such as diabetes, thyroid conditions, some medications, severe trauma, drugs, and alcohol, can all increase the risk of hypothermia.
Prolonged low-core body temperature affects the brain, making it difficult to think clearly or move properly. This makes hypothermia especially dangerous because victims are less likely to know what’s happening to them. Initial symptoms include shivering in adults and older children; clumsy movements; apathy; poor judgment; and cold, pale, or blue-gray skin. Anyone who is not properly clothed or sheltered with adequate heat can become a victim.
If the heat loss is not stopped, hypothermia can quickly lead to unconsciousness and death. The keys to preventing hypothermia are layering clothing to avoid sweating from overheating, staying fueled with high-energy food and fluids, moving to keep extremities warm, and taking frequent breaks out of the cold.
Frostnip, often an early stage of frostbite, may cause numbness or blue-white skin for a short time, but normal feeling and color return when the tissue is warmed; there is no permanent tissue damage.
Frostbite happens when the skin and the tissues under the skin freeze as temperatures fall below 32 degrees F. Commonly affected are the hands, feet, and face. Frostbitten skin begins to look pale or blue and feels cold, numb, and stiff or rubbery to the touch. Longer exposures will affect the top layers of skin, which will feel hard to the touch, then turn red and blister when warmed. When exposure continues, the skin becomes white, blue, or spotty, and feels hard and cold to the touch. As the skin thaws, blood-filled blisters form and turn into thick black scabs. It's likely that some tissue will die; tendons, muscles, nerves, and bones may also be affected.
Most frostbite can be prevented by staying dry and wearing clothing that protects the extremities; insulated boots, thick socks, mittens, and a warm, wind-resistant hat that covers the ears are best.
Nonfreezing cold injuries
Trench foot, chilblains, and Raynaud's Phenomenon are skin and soft-tissue injuries that can result from spending too much time in cold, but not freezing, temperatures. The skin does not actually freeze.
Trench foot happens when blood vessels in wet feet constrict to divert blood to the body’s core; over time – as little as 13 hours – the lack of blood can cause tissue and nerve damage in the heel, toes, or the entire foot. Although cold temperatures can make the condition worse, the cause is prolonged exposure to moisture. Initial symptoms include lack of feeling and red or blue skin resulting from the lack of blood.
Chilblains are small, itchy swellings on the toes, fingers, heels, ears, and nose that usually develop several hours after exposure to the cold as blood vessels near the skin’s surface expand with increased blood flow. This can cause blood to leak into the surrounding tissue, causing it to swell and feel itchy. Affected skin may also turn red or dark blue. Chilblains usually heal completely in a few weeks if further exposure to the cold is avoided. You can reduce the risk of chilblains by gradually warming cold skin. Heating the skin too quickly – in hot water or near a heater, for example – is one of the main causes.
Raynaud’s Phenomenon can be caused by cold temperatures and stress. In either case, blood vessels spasm and block the flow of blood to the affected area – typically the fingers, but any extremity can be affected. The affected area often becomes white, and then turns blue and red as the blood returns over a period that can last from minutes to hours. Numbness and a “pins and needles” sensation may also occur. Staying warm and wearing gloves or mittens may help prevent the onset of cold-triggered Raynaud’s. Raynaud’s can also occur as a “secondary” condition related to other diseases, such as scleroderma, lupus, and rheumatoid arthritis.