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Cooling of body parts may result in various cold injuries - with hypothermia being the most serious. Nonfreezing cold injuries include chilblain, immersion foot and trenchfoot. Freezing injuries include frostnip and frostbite.
Toes, fingers, ears and nose are at greatest risk because these areas do not have major muscles to produce heat. In addition, the body preserves heat by keeping the internal organs warm; thus, reducing the flow of blood to the extremities under cold conditions. In addition, hands and feet tend to get cold more quickly than the body (torso) because:
If the eyes are not protected with goggles in high wind chill conditions, the corneas of the eyes may freeze.
The most severe cold injury is hypothermia which occurs from excessive loss of body heat and the consequent lowering of the inner core temperature (internal temperature of the body). Hypothermia can be fatal.
For more information on the general effects of working in the cold as well as how the body adapts to cold, please see Cold Environments - General.
For information on exposure limits and prevention of injury while working in the cold, please see Cold Environments - Working in the Cold.
Chilblains are a mild cold injury caused by prolonged and repeated exposure for several hours to air temperatures that are cold, but not freezing (from above freezing (0°C or 32°F) to as high as 16°C (or about 60°F)). In the affected skin area there will be redness, swelling, tingling, blisters, and pain. Seek medical help if an infection occurs. Chillblains will usuallly resolve on their own, especially in warmer weather. Recurrence is common for many years.
Immersion foot occurs in individuals whose feet have been wet, but not freezing cold, for days or weeks. It can occur at temperatures up to 10°C (50°F). The primary injury is to nerve and muscle tissue. Symptoms include tingling and numbness; itching, pain, swelling of the legs, feet, or hands; or blisters may develop. The skin may be red initially and turn to blue or purple as the injury progresses. In severe cases, gangrene may develop.
Trenchfoot is "wet cold disease" resulting from prolonged exposure in a damp or wet environment from above the freezing point to about 10°C (50°F). Depending on the temperature, an onset of symptoms may range from several hours to many days but the average is three days. Trenchfoot is more likely to occur at lower temperatures whereas an immersion foot is more likely to occur at higher temperatures and longer exposure times. A similar condition of the hands can occur if a person wears wet gloves for a prolonged period under cold conditions described above. Symptoms are similar to an immersion foot.
Frostnip is the mildest form of a freezing cold injury. It occurs when ear lobes, noses, cheeks, fingers, or toes are exposed to the cold and the top layers of a skin freeze. The skin of the affected area turns paler than the area around it and it may feel pain or stinging, followed by numbness. Skin may also appear shiny and rosy, as well as hardened. The top layer of skin feels hard but the deeper tissue still feels normal (soft). It is a warning that frostbite is beginning.
Frostnip can be prevented by wearing warm clothing and foot wear. It is treated by gentle rewarming (e.g., holding the affected tissue next to unaffected skin of the victim or of another person). As for all cold-induced injuries, never rub the affected parts - ice crystals in the tissue could cause damage if the skin is rubbed. Do not use very hot objects such as hot water bottles to rewarm the area or person.
Frostbite is a common injury caused by exposure to cold or by contact with cold objects (especially those made of metal). It may also occur in normal temperatures from contact with cooled or compressed gases. Skin may look waxy and feel colder than the area around it. It may also be harder to the touch. Blood vessels may be severely and permanently damaged, and blood circulation may stop in the affected tissue. In mild cases, the symptoms include inflammation of the skin in patches accompanied by pain. In severe cases, there could be tissue damage without pain, or there could be burning or prickling sensations resulting in blisters. Frostbitten skin is highly susceptible to infection, and gangrene (local death of soft tissues due to loss of blood supply) may develop.
First aid for frostbite, as well as immersion or trenchfoot, includes:
In moderately cold environments, the body's core temperature does not usually fall more than 1°C to 2°C below the normal 37°C because of the body's ability to adapt. However, in intense cold without adequate clothing, the body is unable to compensate for the heat loss and the body's core temperature starts to fall. The sensation of cold followed by pain in exposed parts of the body is one the first signs of mild hypothermia.
As the temperature continues to drop or as the exposure time increases, the feeling of cold and pain starts to diminish because of increasing numbness (loss of sensation). If no pain can be felt, serious injury can occur without the victim's noticing it.
Next, muscular weakness and drowsiness are experienced. Additional symptoms of hypothermia include interruption of shivering, diminished consciousness and dilated pupils. As hypothermia progresses, severe symptoms may occur, including death.
Canadian Red Cross lists the levels of cold stress to include:
Cold stress (not hypothermic)
Hypothermia is a medical emergency. At the first sign, find medical help immediately. The survival of the victim depends on their co-workers ability to recognize the symptoms of hypothermia. The victim is generally not able to notice his or her own condition.
First aid for hypothermia includes the following steps:
Canadian Red Cross suggests the following supplies for a hypothermia wrap:
When the person has dry or damp clothing, leave the clothing on.
When the person has very wet clothing, if shelter and transport are:
To apply a hypothermia wrap: