Overview

Frostbite is an injury caused by freezing of the skin and underlying tissues. First your skin becomes very cold and red, then numb, hard and pale. Frostbite is most common on the fingers, toes, nose, ears, cheeks and chin. Exposed skin in cold, windy weather is most vulnerable to frostbite. But frostbite can occur on skin covered by gloves or other clothing.

Frostnip, the first stage of frostbite, doesn't cause permanent skin damage. You can treat very mild frostbite with first-aid measures, including rewarming your skin. All other frostbite requires medical attention because it can damage skin, tissues, muscle and bones. Possible complications of severe frostbite include infection and nerve damage.

Symptoms

Signs and symptoms of frostbite include:

  • At first, cold skin and a prickling feeling
  • Numbness
  • Red, white, bluish-white or grayish-yellow skin
  • Hard or waxy-looking skin
  • Clumsiness due to joint and muscle stiffness
  • Blistering after rewarming, in severe cases

Frostbite is most common on the fingers, toes, nose, ears, cheeks and chin. Because of skin numbness, you may not realize you have frostbite until someone else points it out.

Frostbite occurs in several stages:

  • Frostnip. The first stage of frostbite is frostnip. With this mild form of frostbite, your skin pales or turns red and feels very cold. Continued exposure leads to prickling and numbness in the affected area. As your skin warms, you may feel pain and tingling. Frostnip doesn't permanently damage the skin.
  • Superficial frostbite. The second stage of frostbite appears as reddened skin that turns white or pale. The skin may remain soft, but some ice crystals may form in the tissue. Your skin may begin to feel warm — a sign of serious skin involvement. If you treat frostbite with rewarming at this stage, the surface of your skin may appear mottled, blue or purple. And you may notice stinging, burning and swelling. A fluid-filled blister may appear 24 to 36 hours after rewarming the skin.
  • Severe (deep) frostbite. As frostbite progresses, it affects all layers of the skin, including the tissues that lie below. You may experience numbness, losing all sensation of cold, pain or discomfort in the affected area. Joints or muscles may no longer work. Large blisters form 24 to 48 hours after rewarming. Afterward, the area turns black and hard as the tissue dies.

When to see a doctor

Seek medical attention for frostbite if you experience:

  • Signs and symptoms of superficial or deep frostbite — such as white or pale skin, numbness, or blisters
  • Increased pain, swelling, redness or discharge in the area that was frostbitten
  • Fever
  • New, unexplained symptoms

Get emergency medical help if you suspect hypothermia, a condition in which your body loses heat faster than it can be produced. Signs and symptoms of hypothermia include:

  • Intense shivering
  • Slurred speech
  • Drowsiness and loss of coordination

Causes

Frostbite occurs when skin and underlying tissues freeze. The most common cause of frostbite is exposure to cold-weather conditions. But it can also be caused by direct contact with ice, freezing metals or very cold liquids.

Specific conditions that lead to frostbite include:

  • Wearing clothing that isn't suitable for the conditions you're in — for example, it doesn't protect against cold, windy or wet weather or it's too tight.
  • Staying out in the cold and wind too long. Risk increases as air temperature falls below 5 F (minus 15 C), even with low wind speeds. In wind chill of minus 16.6 F (minus 27 C), frostbite can occur on exposed skin in less than 30 minutes.
  • Touching materials such as ice, cold packs or frozen metal.

Risk factors

The following factors increase the risk of frostbite:

  • Medical conditions that affect your ability to feel or respond to cold, such as dehydration, exhaustion, diabetes and poor blood flow in your limbs
  • Alcohol or drug abuse
  • Smoking
  • Fear, panic or mental illness, if it inhibits good judgment or hampers your ability to respond to cold
  • Previous frostbite or cold injury
  • Being an infant or older adult, both of whom may have a harder time producing and retaining body heat
  • Being at high altitude, which reduces the oxygen supply to your skin

Complications

Complications of frostbite include:

  • Increased sensitivity to cold
  • Increased risk of developing frostbite again
  • Long-term numbness in the affected area
  • Changes in the cartilage between the joints (frostbite arthritis)
  • Growth defects in children, if frostbite damages a bone's growth plate
  • Infection
  • Tetanus
  • Gangrene — decay and death of tissue resulting from an interruption of blood flow to the affected area — which can result in amputation

Cold exposure that's severe enough to cause frostbite also can cause hypothermia. When your body temperature drops, your heart, nervous system and other organs don't work correctly. Left untreated, hypothermia eventually leads to complete failure of your heart and respiratory system and to death.

Prevention

Frostbite can be prevented. Here are tips to help you stay safe and warm.

  • Limit time you're outdoors in cold, wet or windy weather. Pay attention to weather forecasts and wind chill readings. In very cold, windy weather, exposed skin can develop frostbite in a matter of minutes.
  • Dress in several layers of loose, warm clothing. Air trapped between the layers of clothing acts as insulation against the cold. Wear windproof and waterproof outer garments to protect against wind, snow and rain. Choose undergarments that wick moisture away from your skin. Change out of wet clothing — particularly gloves, hats and socks — as soon as possible.
  • Wear a hat or headband that fully covers your ears. Heavy woolen or windproof materials make the best headwear for cold protection.
  • Wear mittens rather than gloves. Mittens provide better protection. Or try a thin pair of glove liners made of a wicking material (like polypropylene) under a pair of heavier gloves or mittens.
  • Wear socks and sock liners that fit well, wick moisture and provide insulation. You might also try hand and foot warmers. Be sure the foot warmers don't make your boots too tight, restricting blood flow.
  • Watch for signs of frostbite. Early signs of frostbite include red or pale skin, prickling, and numbness.
  • Plan to protect yourself. When traveling in cold weather, carry emergency supplies and warm clothing in case you become stranded. If you'll be in remote territory, tell others your route and expected return date.
  • Don't drink alcohol if you plan to be outdoors in cold weather. Alcoholic beverages cause your body to lose heat faster.
  • Eat well-balanced meals and stay hydrated. Doing this even before you go out in the cold will help you stay warm. And if you do become cold, drinking warm, sweet beverages, such as hot chocolate, will help you warm up.
  • Keep moving. Exercise can get the blood flowing and help you stay warm, but don't do it to the point of exhaustion.
Oct. 15, 2014
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