Frostbite (congelation in medical terminology) is the medical condition where damage is caused to skin and other tissues due to extreme cold. At or below 59° Fahrenheit (15° Celsius), blood vessels close to the skin start to narrow (constrict). This helps to preserve your core body temperature. In extreme cold or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of your body to dangerously low levels. The combination of cold temperature and poor blood flow can cause tissue injury. Frostbite is most likely to happen in body parts farthest from the heart, and those with a lot of surface area exposed to cold. These areas include the toes, fingers, ears and nose. It is related, but not identical, to hypothermia. The early stages of frostbite are sometimes called "frostnip".
Risk factors include using beta-blockers and having conditions such as diabetes and peripheral neuropathy.
Generally, frostbite is accompanied with discoloration of the skin, along with burning and/or tingling sensations, partial or complete numbness, and possibly intense pain. If the nerves and blood vessels have been severely damaged, gangrene may follow, and amputation may eventually be required. If left untreated, frostbitten skin gradually darkens after a few hours. Skin destroyed by frostbite is completely black and looks loose and flayed, as if burnt.
Move the victim to a warm, safe area. If medical attention is easily reachable, wrap the affected areas with dressings and/or cloths. Also, if it is unlikely that the affected areas can be kept thawed, treatment should not be carried out due to the fact that thawing followed by a second round of freezing can cause more extensive and severe damage to the frostbitten areas. Otherwise, one should place the affected areas in warm (not hot) water, until the areas are soft and sensation has returned. Afterwards, wrap the areas in clean, sterile dressings and attempt to reach medical help (if necessary). If hypothermia has occurred, treat the hypothermia first.
Be aware of factors that can contribute to frostbite, such as extreme cold, wet clothes, high winds, and poor circulation. This can be caused by tight clothing or boots, cramped positions, fatigue, certain medications, smoking, alcohol use, or diseases that affect the blood vessels, such as diabetes.
Wear suitable clothing in cold temperatures and protect susceptible areas. In cold weather, wear mittens (not gloves); wind-proof, water-resistant, many-layered clothing; two pairs of socks (cotton next to skin, then wool); and a scarf and a hat that cover the ears (to avoid substantial heat loss through the scalp).
Before anticipated prolonged exposure to cold, don't drink alcohol or smoke, and get adequate food and rest.
If caught in a severe snowstorm, find shelter early or increase physical activity to maintain body warmth.