Frostbite (congelatio in medical terminology) is the medical condition whereby damage is caused to skin and other tissues due to extreme cold. At or below 0º C (32°F), blood vessels close to the skin start to narrow (constrict). This helps to preserve 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 the body to dangerously low levels. The areas where this occurs will freeze over. The combination of cold temperature and poor blood flow can cause severe tissue injury by freezing the tissue. Frostbite is most likely to happen in body parts farthest from the heart, and those with a lot of surface area exposed to cold. The initial stages of frostbite are sometimes called "frostnip". Mountains or high altitudes with snow are most serious causes of frostbite. If frostbite is not treated immediately then the damage and the frostbite become permanent. Nerve damage will occur due to oxygen deprivation. Frostbitten areas will turn discolored, purplish at first, and soon turn black. After a while nerve damage becomes so great that feeling is lost in the frostbitten areas. Blisters will also occur. If feeling is lost in the damaged area, checking it for cuts and breaks in the skin is vital. Infected open skin can lead to gangrene and amputation may be needed.
The use of hyperbaric oxygen therapy as an adjunctive therapy can assist in the salvaging of a greater amount of tissue by increasing the viability of cells bordering necrotic tissue by preventing hypoxia and reducing edema. There have been case reports but few actual research studies to show the effectiveness.
Moreover employees working in chemical laboratories should take precautions to wear gloves and other safety equipment as liquid Nitrogen and other cryogenic liquids can cause frostbite even with brief exposure.
If caught in a severe snowstorm, one should find shelter early or increase physical activity to maintain body warmth.
People susceptible to frostbite should wear woolen socks/gloves/caps in extreme cold. For frostbite in the feet, keeping feet in warm saline water will provide relief. Diabetes can also sometimes lead to frostbite, so diabetics should take precautions as to avoid trips to ice-cold places.