Frostbite

Frostbite is damage to skin and tissue caused by exposure to freezing temperatures – typically any temperature below minus 0.55C (31F).

Introduction

Frostbite is damage to skin and tissue caused by exposure to freezing temperatures – typically any temperature below minus 0.55C (31F).

Frostbite can affect any part of your body. However, the extremities – such as the hands, feet, ears, nose and lips – are most likely to be affected.

The symptoms of frostbite are varied, but usually begin with the affected parts feeling cold and painful. If exposure to the cold continues, you may feel pins and needles before the area becomes numb as the tissues freeze.

The severity of frostbite and how quickly it develops depends on how cold it is and the length of exposure.

The effects of frostbite range from minor tissue damage that fully recovers without treatment to severe tissue loss that requires surgery or even amputation to remove dead tissues.

Read more about the symptoms of frostbite.

If the symptoms are more severe, go immediately to your nearest accident and emergency department.

Treating frostbite

It is important that a person with frostbite is taken to a warm environment as soon as it is safe to do so, as they are also likely to have hypothermia. Do not put pressure on the frostbitten area.

The affected area should be re-warmed slowly by immersing it in warm (but not hot) water. However, do this only if there is no possibility of further freezing. If re-warmed tissue becomes frozen again, there will be further tissue damage.

A bath of water at 40-41C (104-105.8F) is recommended for re-warming. This process may be very painful and large amounts of painkillers are often required. Ideally, re-warming should be performed by trained medical professionals.

Read more about treating frostbite.

Preventing frostbite

Almost all cases of frostbite can be prevented by:

  • wearing appropriate clothing – multiple layers of warm, loose clothing are better than a single layer
  • wearing a weatherproof hat that covers your ears – a surprising amount of heat can be lost through your head
  • avoiding unnecessary exposure to cold
  • keeping dry – remove any wet clothing
  • planning for emergencies – for example making sure you keep a warm blanket and some spare clothes if driving in icy conditions in case you break down

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Who’s at risk of frostbite?

Certain groups of people are at greater risk of getting frostbite. They include:

  • people who take part in winter and high-altitude sports, such mountaineers and skiers
  • anyone stranded in extreme cold weather conditions
  • anyone with a job that means they are outdoors in harsh conditions for a long time, such as soldiers, sailors and rescue workers
  • homeless people
  • the very young and very old, as their bodies are less able to regulate body temperature
  • people with conditions that cause blood vessel damage or circulation problems, such as diabetes and Raynaud’s phenomenon
  • anyone taking medications that constrict the blood vessels, including beta blockers (smoking can also constrict the blood vessels)

Many cases of frostbite occur in people who have taken drugs or drunk alcohol and who fall asleep outside in cold weather.

Read more the causes of frostbite.

Complications

Complications of frostbite can be serious and include:

  • a life-threatening drop in body temperature (hypothermia)
  • the affected body part becoming particularly vulnerable to infections, such as tetanus
  • long-term pain

Read more about the complications of frostbite.

Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Symptoms

The symptoms of frostbite progress in stages. The longer the body is exposed to freezing conditions and the colder the temperature is, the more advanced frostbite can become.

Early stage – frostnip

During the early stage of frostbite, you will have pins and needles, throbbing or aching in the affected area. The skin will become cold, numb and white, and you may feel a tingling sensation.

This stage of frostbite is also known as frostnip, and is common in people who live or work in cold climates. The extremities, such as the fingers, nose, ears and toes, are most commonly affected.

Intermediate stage

After these early signs, prolonged exposure to cold temperatures will cause more tissue damage. The affected area will feel hard and frozen. When you are out of the cold and the tissue is thawed out, the skin will turn red and blister, which can be painful. There may also be swelling and itching.

This is known as superficial frostbite because it affects the top layers of skin and tissue. The skin underneath the blisters is usually still intact but treatment is needed to make sure there is no lasting damage.

Advanced stage

When exposure to the cold continues, frostbite becomes increasingly severe. The skin becomes white, blue or blotchy, and the tissue underneath feels hard and cold to touch. There may be further damage to tendons, muscles, nerves and bones beneath the skin.

This is known as deep frostbite and requires urgent medical attention.

As the skin thaws, blood-filled blisters form and turn into thick black scabs. At this stage, it is likely that some tissue has died. This is known as tissue necrosis, and the tissue may have to be removed to prevent infection.

Long-term effects

People with a history of severe frostbite often report further long-term effects of frostbite.

These can include:

  • increased sensitivity to cold
  • numbness in the affected body parts, most commonly the fingers
  • reduced sense of touch in the affected body part
  • persistent pain in the affected body part

Numbness refers to a lack of sensation in a part of the body.

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Causes

Frostbite occurs when your body is exposed to low temperatures. The severity of frostbite depends on how cold the temperature is and how long you are exposed for.

Severe weather conditions (such as blizzards), wind chill and how suitable and dry your clothing is can all affect the development of frostbite.

Damage to the skin and tissue is caused by the body’s response to extreme cold. When it’s cold, blood flow to the extremities – such as the hands, feet, ears, nose and lips – slows down as blood vessels narrow.

This allows an increase in the flow of blood to the body’s vital organs to keep the body alive. As blood is redirected away from the extremities, these parts of the body get colder. Fluid in the tissue freezes and ice crystals form. These crystals can cause severe damage to the cells and tissues in the area and the blood flow may be significantly compromised. The low blood flow deprives the tissues of oxygen, eventually leading to the death of the tissues if blood flow cannot be restored.

Prolonged exposure to the cold can cause further damage. The greatest damage occurs in tissues that freeze, thaw, and then re-freeze.

Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Diagnosis

The doctor carrying out the diagnosis, who may be your doctor or a doctor at accident and emergency, will want to know how you became frostbitten as this can provide information on the likely extent of any damage.

You may be asked:

  • Where did the injury occur?
  • What was the temperature at the time of the injury?
  • How long were you exposed to the cold?
  • Were there any factors that could have made the injury worse, such as wind chill or wearing wet clothing?

The doctor will then examine the affected body part. The full extent of a frostbite injury is often not apparent until a few days after the injury occurs. So you may be asked to stay in hospital for observation or return for a follow-up appointment.

Your doctor may take a photo of the injury (with your permission) and email it to a specialist with experience in diagnosing frostbite.

In cases of severe frostbite, imaging studies may be required to check the extent of injury to the bones, blood vessels and nerves.

Imaging studies that can be used in this way include:

  • X-rays
  • bone scans – a small amount of radioactive material is injected into your veins, and damaged areas of bone will absorb more of the radiation, which can show up on the scanner
  • magnetic resonance imaging (MRI) scan – where a strong magnetic field and radio waves are used to produce detailed pictures of the inside of affected areas of the body

Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.

Treatment

Preventing frostbite, by taking the necessary precautions before it occurs, should always be a priority. If you suspect you have frostbite, seek medical attention immediately.

If the symptoms of frostbite are minor, call your doctor.

If it’s more severe, go immediately to your nearest accident and emergency department or call for an ambulance if you cannot move.

See symptoms of frostbite for more information about the stages of frostbite.

If medical assistance is not available, steps can be taken to treat frostbite:

  • If possible, move to a warmer place – it’s best to avoid walking on frostbitten toes and feet as this can cause further damage, although in emergency situations this may not always be possible.
  • Replace wet clothing with soft, dry clothing to stop further heat loss.
  • Warm the body by wrapping it in blankets and protecting the frostbitten parts.
  • Do not rub the affected area or apply direct heat (such as from a fire or heater) as this can cause further injury.

Re-warming

The affected areas need to be re-warmed. Do not try to do this until you are out of the cold. If the warming process is started and the frozen parts are re-exposed to the cold, it can cause further, irreversible damage.

Ideally, re-warming should be done under medical supervision because:

  • it can be a painful process that requires access to painkillers
  • the best results are achieved using a whirlpool bath that contains a mild antiseptic

The affected area should be re-warmed slowly by immersing it in warm (but not hot) water. A bath of water at a temperature of 40-41C (104-105.8F) is recommended.

Re-warming should last at least 30 minutes and should only be stopped once the affected body part has a red-purple colour and can be easily moved.

This process can be repeated twice a day until there are clear signs that the affected body part is beginning to heal, such as the growth of new skin and the return of normal skin colour.

As re-warming can often be painful, painkillers may be required. Depending on the extent of the pain, this could be over-the-counter painkillers such as ibuprofen or very strong painkillers such as morphine.

After re-warming

After the frostbitten area has been thawed, it should be wrapped very gently in clean bandages, with the fingers and toes separated out. It is very important to keep the skin clean to avoid infection. Too much movement should be avoided, and the limbs should be elevated if possible. Avoid walking on affected parts that have been re-warmed as the tissues will be very delicate.

After re-warming, the skin will be discoloured and blistered. It will eventually scab over. If the frostbite is superficial, new pink skin will form beneath the discoloured skin and scabs. The area usually recovers within six months.

Severe frostbite

In cases of severe frostbite, you will need to be admitted to a specialist unit that has experience in treating these sorts of injuries.

This is often a specialist burns unit, as exposure to very high temperatures can cause the same sort of injury as exposure to very cold temperatures.

If it is thought that there is a very high risk of major damage, you may be given a type of treatment called thrombolysis. This involves giving you injections or medication through a drip in your arm that helps to break up small clots in the frostbitten blood vessels. This should help improve blood flow to the affected body part, which can help stimulate healing and prevent more damage.

You may also be given antibiotics to prevent the affected body part from becoming infected.

If some of the tissue of the affected body part has died, it will need to be removed. This is known as debridement. In the most serious cases, it is necessary to remove an entire part of the body, such as toes or fingers. This is known as amputation.

A decision to perform debridement or amputation is normally delayed for several weeks as often what appeared to be dead tissue can heal and recover over time.

Long-term effects

Some people are left with permanent problems after frostbite, such as increased sensitivity to cold, numbness, stiffness and pain in the affected area.

Not much can be done to treat sensitivity to cold, numbness or stiffness.

A medication called amitriptyline can sometimes be effective in controlling the pain associated with long-term effects of frostbite.

Numbness refers to a lack of sensation in a part of the body.

Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.

Complications

Infection and hypothermia are the main complications of frostbite.

Hypothermia

Around 1 in 8 people with severe frostbite will also develop hypothermia.

Hypothermia occurs when a person's body temperature drops below 35C (95F). Initial symptoms can include:

  • constant shivering
  • tiredness
  • low energy
  • cold or pale skin
  • fast breathing

Symptoms of severe hypothermia include:

  • unconsciousness
  • shallow or no breathing
  • weak, irregular or no pulse
  • dilated pupils

Hypothermia is treated by preventing further heat being lost and by gently warming the patient. Seek immediate medical attention if you think you or someone else has severe hypothermia as it can be life threatening.

Read more about the treatment of hypothermia.

Infection

If some of your tissue dies, the dead tissue will no longer have a blood supply. This can make the affected body part very vulnerable to infection as your body relies on white blood cells to ward off infections.

Infections associated with frostbite include tetanus and more generalised bacterial wound infections.

More seriously, infection can spread into the blood (sepsis).

These conditions require admission to hospital and treatment with immunoglobulin in the case of tetanus and antibiotics in the case of sepsis.

Read more about treating tetanus and treating sepsis.

Prevention

Frostbite can occur very rapidly at temperatures below freezing. If you spend any length of time exposed to extreme cold, it's vital to ensure that your skin is well protected.

If you are at high risk of frostbite, remember that extreme cold has a numbing effect. This means that your skin and tissue may freeze without you realising. It is important to recognise the tingling sensation of frostnip that may lead to the early symptoms of frostbite.

If you are going to be in cold temperatures for any length of time, your choice of clothing is very important. Make sure that your extremities, such as your hands, feet, nose, ears and lips, are well protected. These are the most vulnerable areas and often the first to be affected. A warm hat, well-insulated boots and a thick pair of well-fitting socks are all essential. Mitts provide better protection against very cold weather than gloves.

Wearing several thin layers is more effective than wearing one thick one. Thin layers trap air that warms your body's temperature and acts as extra insulation. Your clothes should fit well, and each layer of clothing should be larger than the one below to prevent pressure and constriction.

If you're travelling in very cold weather, make sure you are adequately prepared for an emergency. If you're travelling by car, have a warm blanket and some spare clothes in case your car breaks down.

If travelling by foot, always let others know where you are going and have a fully charged mobile phone in case of a fall or other accident.

Avoiding drinking alcohol in very cold weather. Aside from the risk of falling asleep in the cold when drunk (which is a common cause of frostbite), alcohol causes you to lose heat at a faster rate.

Healthy warm meals and drinks, such as hot chocolate, are effective in keeping you warm.

The combination of wind and cold temperature (wind chill) can cause a rapid drop in temperature, so avoid exposing yourself to the wind when possible.

Do not smoke in very cold conditions as nicotine can narrow your blood vessels, making you more vulnerable to the effects of the cold.

Similarly, people with conditions known to affect the blood vessels, such as Raynaud’s phenomenon, need to take extra precautions to protect themselves from the harmful effects of the cold.

Content supplied by NHS Choices