Winter cold and snow provide a number of opportunities to get outside and participate in activities such as skiing, sledding and snowmobiling. However, without proper protection, cold injuries, such as frostbite, can occur even when the temperature is above freezing (32 degrees F, 0 degrees C). This is especially true if there is a high wind or if a glove or sock gets wet. The information below describes these types of cold injuries as well as what to do to prevent and treat them prior to reaching a healthcare provider.
What type of injuries can be caused by the cold?
Cold injuries are divided into two general groups: those that occur without any freezing of the body tissues and those that result from the freezing of the skin or a body part (generally the fingers, toes, ears or nose). Examples of cold injuries without tissue freezing include chilblains and “trench foot.” Frostbite is a cold injury that is associated with tissue freezing.
Cold Injury Without Tissue Freezing
Chilblains is the most common type of cold injury and occurs when there is exposure of the affected area to a dry cold. There is no tissue freezing with a chilblain injury. If you have chilblains, you might notice that the affected area may itch, turn reddish-blue, and be swollen and painful. With time, blisters containing clear fluid may form. The injured area may be very sensitive to the cold in the future. However, there is usually no other permanent damage.
Trench Foot (Immersion Injury)
The cold injury called “trench foot” was named after the condition suffered by many soldiers in the trenches during World War I. “Trench foot,” also known as immersion injury, occurs when a body part is exposed to a cold, wet environment. This type of injury may occur when a glove or sock becomes wet. As with chilblains, the affected area is not frozen. The symptoms of immersion injury are similar to those of chilblains, but the damage is usually more serious. The blisters are deeper and resemble the blisters that form after a burn. Again, there is no permanent injury other than cold sensitivity.
Cold Injury with Tissue Freezing
Frostbite occurs when there is freezing of the injured area. When an area of the body freezes, ice crystals form within the cells. These ice crystals cause the cells to rupture, leading to cell death.
Frostbite goes through several stages. When only the surface skin is frozen, the injury is called “frostnip” (a first degree injury). Frostnip begins similarly to chilblains with itching and pain. The skin then “blanches” or looses its blood supply. Eventually, the area loses feeling and becomes numb. Frostnip generally does not lead to permanent damage because only the top layers of skin are involved. Long-term sensitivity to cold can occur from frostnip.
If the freezing continues, the skin may become frozen and hard (a second degree injury). However, the deep tissues of the affected part are spared and remain soft and normal. This type of injury generally blisters 1-2 days after freezing. The blisters may become hard and blackened. However, they usually look worse than they are. Most of these injuries heal over 3-4 weeks. Again, the affected area may remain sensitive to heat and cold permanently. Should blistering occur, the injury should be seen by a healthcare practitioner.
If further freezing continues, a deep frostbite occurs (a third or fourth degree injury). When this occurs, all of the muscles, tendons, blood vessels, and nerves of the affected extremity are frozen. The extremity is hardened, feels woody, and use of the involved part is lost temporarily, and in severe cases, even permanently. The involved area is deep purple or red with blisters; usually these blisters are filled with blood. It is this type of severe frostbite that results in lost fingers and toes. However, it can take several months to determine how much damage has actually occurred in the freezing process. For this reason, surgery to remove tissue that is not capable of surviving is frequently delayed.
Who is most likely to get a cold injury and what can be done to prevent it?
Anybody can develop a cold-related injury, but the young and the elderly are especially prone to this type of injury. In the young, the small size of their extremities makes them more likely to freeze. In the elderly, poor circulation may contribute. In both of these groups, mobility may be limited and the cold injury occurs before the person is able to move indoors. Certain drugs, such as alcohol and other drugs or medications that depress the ability to feel accurately, make it more likely that the individual will develop a cold injury. These drugs make it less likely that a person will recognize that he or she is in danger of becoming frostbitten. Alcohol also causes the skin to flush, allowing warm blood to become cooled at the surface of the skin. Additionally, any underlying illnesses which are characterized by poor circulation, such as diabetes, hypothyroidism (low thyroid), and arteriosclerosis, can make it more likely that one will develop a cold injury.
The best way to prevent a cold injury is to dress warmly and move indoors once your fingers or toes begin to feel cold. Always keep your hands and feet dry and your ears covered. Several drugs have been tried to help prevent frostbite. One of the most commonly used drugs is nifedipine (Procardia). Nifedipine increases circulation to the extremities by dilating the blood vessels. While it makes sense that it would help prevent frostbite, all of the evidence is anecdotal. No studies have been conducted to determine whether or not nifedipine prevents frostbite. Beta-blockers (Lopressor, Tenormin, Inderal, and others), which are often used to treat high blood pressure and heart disease, reduce the circulation to the hands and feet. These medications are more likely to contribute to the problem of frostbite.
How should frostbite and other cold injuries be treated?
It is important not to thaw the extremity if there is a risk of it re-freezing!! As was mentioned above, injury is caused when ice crystals form in the cells. For this reason, it is better to leave the part frozen until it will remain thawed when warmed. Re-freezing will only lead to more severe damage. If you are camping and unable to get indoors, leave the extremity frozen.
The best way to warm a frozen part or one that has a chilblain or trench foot (immersion injury) is to put it into a tub of hot water (104-108 degrees F (40-42 degrees C)). Make sure to test the temperature of the water with a thermometer or a hand that is not frozen!! It is important to avoid burning the injured area (which may lack feeling). There may be quite a bit of pain when the injured area is re-warmed. Acetaminophen (Tylenol and others), aspirin (Bayer and others), naproxen (Aleve and others) or ibuprofen (Advil and others) may be used to help the discomfort. If stronger pain control measures are required, contact your health care practitioner.
One common “folk remedy” is to rub the extremity with snow; this should be avoided. Any rubbing may aggravate the injury. The injured tissue can be fragile and must be handled gently. Warming over a fire or next to a heater should also be avoided. These methods have a high risk of burns and tend to dry out the injured tissue, thereby causing more damage.
When should I seek medical care?
Chilblains can usually be treated at home. However, if you have a true frostbite injury or any blistering of the injured part, it should be seen by a healthcare professional, such as a physician or physician’s assistant. If there is any sign of infection (increasing redness, warmth, etc.), a healthcare professional’s care should be sought. Lastly, if there is a lot of blistering and you are not up to date on your tetanus shot (within the last 10 years), you should receive a tetanus booster.
If you are unable to obtain medical care chilblains, try to leave the blisters intact. As long as they remain closed, it is unlikely that they will become infected. Once opened, make sure that the blisters drain freely and trim off any dead tissue with a sterile pair of scissors. Keep any open areas clean and covered. A first aid cream, such as Bacitracin ointment, may be used. Seek medical care as soon as possible. Trench foot (immersion injury) and frostbite should be evaluated by a healthcare practitioner. These injuries can require long-term evaluation for complications and treatment.
Frostbite & Other Cold Injuries At A Glance
- Cold injuries occur with and without freezing of body tissues.
- The young and the elderly are especially prone to cold injury.
- Alcohol increases the risk of cold injury.
- Examples of cold injuries include chilblains, “trench foot,” and frostbite.
- Frostbite can lead to loss of body parts.
- It is important not to thaw an extremity if there is a risk of it re-freezing.
Revision date: June 11, 2011
Last revised: by Tatiana Kuznetsova, D.M.D.