Frostbite

Medically Reviewed by Jabeen Begum, MD on January 03, 2024
Written by Lori M. King, PhD
9 min read

Frostbite is an injury to your skin and potentially your underlying tissues. It's caused by exposure to freezing temperatures. It can affect any part of your body, but it's more common in your fingers, toes, nose, ears, cheeks, and chin. This is because these areas have less insulation and blood flow, which allows ice crystals to form in these tissues faster than in other areas of your body. Ice crystals cause much of the damage from frostbite.

Frostbite can cause permanent damage to your body, and if it's severe, you may need to have the frostbitten body part amputated (surgically removed from your body).

What is frostnip?

Frostnip is a mild form of frostbite that doesn't cause permanent damage to your skin. In people with light skin tones who have frostnip, your skin may look red or purple. Skin color changes may be hard to see in people with dark skin tones, but your skin may look lighter than your natural tone. Also, your skin may feel cold, painful, and tingly.

Frostnip is an early warning sign of frostbite. If you have signs or symptoms of frostnip, get inside as soon as you can and thaw your skin with warm (not hot) water. After you thaw your skin, you may get small red bumps (chilblains).

Symptoms include:

  • Cold skin and a tingly feeling (at first)
  • Numbness
  • Depending on your usual skin tone and how bad your frostbite is, your skin may look red, white, blue-white, gray-yellow, purple, brown, or ashy (rough, bumpy, dry, and possibly with thin, cracked lines)
  • Hard or waxy (thick, tight, shiny, and smooth) skin
  • Clumsiness because of joint and muscle stiffness
  • Blisters may form when you rewarm your skin

You can get frostbite before you realize it because as it gets worse, your skin goes numb. So, you may have damage that you can't feel. That's why you need to look for changes in the way your skin looks.

What does frostbite look like?

Your skin may change colors. For instance, it may look white, gray-yellow, or lighter than your normal skin tone. Your skin may also look waxy. When you rewarm the area, your skin may become swollen and painful. 

Blisters generally form within 4-6 hours. If the blisters fill with clear fluid, that suggests superficial damage. In this case, you likely won't lose any of your tissue. If the blisters fill with blood, that suggests deeper damage, and you may lose some of your damaged tissue. Deep tissue damage may lead to dry gangrene with a hard black cover (carapace) over your damaged tissues. Depending on where you have frostbite, severely damaged tissue may even shrink and fall off on its own (autoamputation).

There are three stages. Early frostbite affects the top layers of the skin. More advanced cases can go all the way to the muscles and bones.

Frostnip (early stage)

  • Your skin changes color (depending on your natural skin tone, it may look red, purple, or lighter than normal)
  • Your skin may itch, sting, burn, or feel like “pins and needles”
  • After rewarming your skin, you may get chilblains

Superficial frostbite

  • Your skin may sting or swell
  • Your skin may become hard and may look shiny or waxy
  • When your skin thaws, you may get painful patches that look like a bruise
  • Your skin may also peel and hurt like a sunburn, and you may get blisters after 1-2 days

Severe (deep) frostbite

  • Your skin may be completely numb, and it may be difficult to move that area or move it normally
  • You may lose all sensation in the frostbitten area, and your joints and muscles may stop working
  • Your skin may become hard and black and may also fall off
  • You may get large blisters 2-4 days after your skin thaws

Call 911 and go to the ER if:

  • You have any signs or symptoms of superficial or deep frostbite (skin color and texture changes, pain, numbness, and blisters).
  • You show signs of hypothermia, such as intense shivering, slurred speech, drowsiness, and loss of coordination.

 

Your body responds to cold temperatures by closing your blood vessels. This lowers blood flow to your extremities, including your hands, fingers, feet, and toes, so that your body can pump more blood and oxygen to your internal organs. As blood flow and oxygen levels in your extremities decrease, the area gets colder and colder until ice crystals form. Ice crystals can cause serious damage to your cells and tissues. In severe frostbite, the damage may be so bad that you develop gangrene.

Gangrene is when your body tissues die because the blood supply is cut off (dry gangrene) and bacteria invade the tissue (wet gangrene). Severe frostbite usually causes dry gangrene.

Frostbite injuries are caused by:

  • Direct damage from the cold
  • Indirect damage caused by dehydration, as fluid and electrolytes flow out of your damaged cells
  • Ice crystals that form in your blood vessels and cells
  • Decreased blood flow in the area due to cold and cell damage
  • Swelling after rewarming causes blood clots and further decreases blood flow in the area

You’re more likely to get frostbite if your clothes don't protect you against the cold, or if it's windy and/or wet.

Frostbite temperature

Frostbite happens at temperatures below freezing (32 F). However, wind may make the temperature much colder, which increases your chance of frostbite.

How long does it take to get frostbite?

How soon frostbite happens depends on how cold and windy it is outside. When the wind chill is −15 F, you can get frostbite on exposed skin in less than 30 minutes.

Some factors that increase your risk of frostbite include:

  • Cold weather
  • No (or inadequate) shelter from the cold
  • High wind chill factor
  • Being out in cold, windy, and/or wet conditions for an extended period
  • Living in a high-altitude area
  • Medical conditions that affect your ability to feel or respond to cold or lower your blood circulation, such as malnutrition, dehydration, sweating a lot, diabetes, hypothyroidism, or stroke
  • Alcohol or drugs
  • Smoking
  • Mental condition that impairs your judgment, such as panic disorder
  • History of frostbite or cold injuries
  • Being older than 65 years (infants are also at high risk of frostbite)

There’s no specific test for frostbite. It's diagnosed based on your signs and symptoms.

Your doctor will ask how long you were out in the cold and what the temperature was. They’ll look closely at your skin and may recommend an x-ray or another kind of scan to see if there’s any serious damage to your bones or muscles. If you have severe frostbite, they may also order other tests, such as Technetium-99 scan or magnetic resonance angiography (MRA), to help them tell if you need an amputation and how much of your tissue needs to be amputated.

Frostbite home care

  • Get to a warm place out of the wind as soon as possible and remove any wet clothes.

  • Protect the frostbitten area from more exposure to the cold.

  • If possible, don't walk if your feet or toes are frostbitten. If you have to walk to get care, don't thaw your feet until you're in a place where you don't have to walk. Thawed tissue is more easily injured than frozen tissue. Allowing your tissue to thaw and then refreeze can cause more serious damage. If possible, clean, dry, and wrap any frozen areas with a sterile cloth.

  • Don't rub or massage the area because this can cause more damage.

  • Put the frostbitten area in warm (not hot) water. The water should be comfortable to the touch on skin that isn't frostbitten. Ideally, use water that's at body temperature -- 98.6 F and no warmer than 102 F. If you don't have warm water, rewarm the area with body heat. For instance, put your frostbitten fingers in your armpit. Don't rewarm with a heating pad, heat lamp, stove, fireplace, or radiator. Your skin will be numb and you could burn yourself without realizing it.

  • Take over-the-counter pain relievers.

Frostbite hospital care

At the hospital, your health care team will likely take the following steps:

  • Raise your core body temperature using warm IV fluids if you have hypothermia.
  • Warm you, usually with warm water baths.
  • Encourage you to move the affected body part as it thaws. Your doctor will examine your body part as it thaws to tell if you can move it or feel with it.
  • Give you pain medicine. Depending on the severity of frostbite, your pain may be severe.
  • If your affected part doesn't have blood flow after it thaws, your doctor may give you medicine, such as papaverine, nicardipine, or nitroglycerin, to get your blood flowing in that area.
  • Give you medicine to prevent an infection.
  • Give you a tetanus booster.

If you have severe frostbite, your doctor may watch your injury for several weeks before they can tell if you need tissue surgically removed, and, if so, how much needs to be removed.

Caring for someone with frostbite

If you notice signs of frostbite on someone else, get the person to a warm place out of the wind as soon as possible. Remove any wet clothes. Don't rub the frostbitten area. If it's possible to keep them warm, thaw their injury with warm water or your body heat. Get them to the ER as soon as possible, especially if they have any signs of hypothermia.

If you have frostbite, you may develop intolerance to cold in that area. This may be because the cold injury has caused permanent damage to your blood vessels and your autonomic nervous system. Your autonomic nervous system manages your body processes, such as blood pressure, body temperature, breathing, digestion, heart rate, and sweating.

You may also get a condition called complex regional pain syndrome (CRPS). This is a condition that causes pain, changes in your skin color or texture, decreased function in the affected limb, and changes in the way your hair and nails grow in the injured area. This may be due to permanent nerve damage.

Complications may also include:

  • A feeling of tingling, numbness, or “pins and needles”
  • Loss of your nails
  • Reduced or increased sweating
  • Cracked skin
  • Wasted muscles
  • Long-term pain or phantom pain
  • Joint stiffness
  • Tremors

If possible, avoid going outside or limit your time to 10-15 minutes when it's cold and/or windy. Pay attention to temperature forecasts and wind chill readings.

If you know you will be out in the cold, wear appropriate clothes, such as multiple layers of light, loose-fitting clothes. These layers will act as insulation and keep you warm. Don't wear clothes or boots that are tight enough to cut off your circulation because this can increase your risk of frostbite. Make sure that snow can't get in any of your layers.

You'll want three layers of loose clothes:

  • The first should be made of a material that helps keep you dry, such as moisture-wicking thermal underwear.
  • The second goes over the first and should be made of an insulating material such as wool or fleece.
  • The third should be worn on top and should be windproof and waterproof.

Take care to protect your extremities:

  • Wear two pairs of socks: a moisture-wicking pair close to your skin and a thick pair of wool or wool-blend socks over those.
  • Wear waterproof, insulated boots that cover your ankles.
  • Wear mittens on your hands because these protect your fingers better than gloves.
  • Wear a warm, weatherproof hat that covers your ears.
  • Cover your face with a scarf or face mask. This will keep the air you breathe warm and help prevent frostbite on your nose and face.

Other measures that can help include:

  • Remove any wet clothes, especially gloves or mittens, hats, and socks, as soon as possible.
  • Don't drink alcohol if you're going out in cold weather. Alcohol causes you to lose body heat faster.
  • Don't smoke because this narrows your blood vessels and increases your risk of frostbite.
  • Watch yourself and others for signs of frostnip. Get someplace warm and dry if you notice any of these signs.
  • Stay hydrated.
  • If you're driving in cold weather, keep a warm blanket, some spare clothes, a first aid kit, and food and water in your car in case you break down.
  • If you're walking in the cold, tell someone where you're going and when you'll be back, and take a fully charged mobile phone with you in case you have an accident.