Frostbite

Patient education about frostbite of the hands and fingers, symptoms, treatment, prevention, and recovery.

Clear or milky blisters on the hand from mild to moderate frostbite
Figure 1. Clear or milky blisters are a sign of mild to moderate frostbite.

Frostbite is a limb injury caused by freezing. In cold temperatures, the body constricts the blood vessels in the limbs to try to keep the core warm. Frostnip occurs before freezing, as skin of the fingers and hands may become red, then pale and numb. Warming the tissues correctly before freezing can prevent loss of tissue. If the cold exposure continues, frostbite can follow, and the injury can cause permanent damage or even finger loss.

During frostbite, the freezing of tissues leads to the creation of damaging ice crystals inside the body. First, the crystals form between cells. This can progress to ice forming inside the cells, which causes further damage. First, the skin layers are affected. With more cold exposure, there can be damage to deeper tissues including bone. The longer the tissues are frozen, the higher chance of severe damage.

When cooled, blood can thicken or clot. This damages the blood vessel lining. Rewarming too fast can also cause injury to the tissues. Frostbite in hands can be mild to severe and requires treatment, often in a hospital. When the injury is significant enough, amputation may be required even after the best treatments.

Problems can persist for months, even a lifetime, after frostbite. These may involve chronic pain and/or numbness, finger sweating, and skin or nail changes. The area may also be more sensitive to cold in the future and develop arthritis from the loss of good cartilage cells in the joints.

Causes

Frostbite happens when the fingers or hands are exposed to freezing conditions for too long. Lack of proper clothing, homelessness, and cold exposure during military service are common risk factors.

Some conditions may limit a person’s ability to move away from exposures or make the fingers more vulnerable to damage from the cold. Examples include alcohol or drug abuse, diabetes, mental illness, poor nutrition, or dehydration. Some studies have reported that children, people of African descent, and smokers are more likely to suffer frostbite. Fingers damaged by prior frostbite are also at higher risk for new injury.

Hand with deeper frostbite injury and blood or blue colored blisters
Figure 2. Blisters with blood or blue color are a sign of deeper, more severe injury due to frostbite.

Signs and Symptoms

Before frostbite occurs, you may see symptoms of frostnip. The skin may become pale or waxy in color. This is due to blood vessel spasm. The fingers or hand typically become numb. With these early symptoms of frostnip, the damage is typically reversible.

When the skin actually freezes, it officially becomes frostbite. The skin then becomes firm due to ice crystals forming in the skin. Swelling, also called edema, usually occurs when fluid leaks from the damaged cells and blood vessels. If there is longer exposure, deeper tissues may also freeze, release toxins from dying cells into the body, and eventually stop functioning.

Depending on the severity of frostbite, symptoms may include:

  • Blisters: Clear or milky blisters are a sign of mild to moderate frostbite. Bloody or blue blisters are a sign of deeper, more severe injury. These blisters may form during the first 24 hours.
  • Black hard covering: With more severe frostbite, the area may turn black, which means some tissue has died.

When exposed to prolonged freezing conditions, the human body can lose its normal internal temperature and become unable to function. This is called hypothermia and can lead to death. Signs of hypothermia include the person becoming confused, clumsy, and having a slow pulse.

Severe frostbite with black hard tissue covering on fingers
Figure 3. A black, hard covering is a sign of severe frostbite when tissue has died.

Treatment

Treatment of frostbite starts by first treating hypothermia. Treatment for hypothermia is primarily providing shelter from cold exposure. Then the person can be changed into warm, dry clothing and given warm fluids by mouth. Treatment of hypothermia is lifesaving.

Many times, when frostbite occurs, it is not easy to get the individual to a hospital quickly enough. The best course of action is to take the initial treatment step yourself before medical personnel can arrive or before you can get to a hospital. This includes limiting exposure to further cold and protecting the frozen body part from more damage by wrapping it in a warm or room-temperature dry covering.

Ibuprofen or aspirin can be given before transport to a medical facility. It is not recommended to put high heat on the damaged body part if you are able to get to a medical facility within two hours. Immediate high heat can further damage numb fingers. Use of heaters, fire, or car exhaust should not be tried.

Rubbing the affected parts with snow or ice should not be done. These treatment myths can cause additional damage. Do not allow the affected body part to thaw and refreeze before or during transport to medical care because the results are usually much worse.

Medical rewarming and hospital care

Once under the supervision of a medical professional, the best treatment for frostbitten fingers or hands is to rewarm in a warm water bath, about 98 to 102 degrees Fahrenheit. This is done until the affected part has become red and soft, usually about 15 to 30 minutes or longer.

During rewarming, there is initially more cellular injury. This is due to blood thrombosis, or clotting, and damage to the blood vessel linings. The damage due to these changes is called reperfusion injury. Pain during rewarming may require narcotics. The degree of frostbite injury usually cannot be assessed fully until rewarming and reperfusion are complete.

When blisters form, treatment at a hospital is usually required and may last for weeks or longer. Sometimes, medications are used to open the blood vessels or break up blood clots. These are usually only used during the first 24 to 48 hours. Additional treatments of the healing fingers include whirlpool baths, elevation, and medicine for inflammation.

Recovery and Prevention

After frostbite, the fingers may be stiff, and hand therapy is used to help them move again. However, loss of full hand use may remain for the patient’s lifetime. Severe frostbite that affects the deeper tissues can even lead to amputation.

Prevention is considered the best treatment for frostbite. Frostbite in hands, even after getting medical care, can result in problems for months or even for a lifetime.

Figures 1-3 courtesy of James E. O’Malley, MD.