Overview

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

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

The symptoms of frostbite 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.

When to seek medical attention

If you think you or someone else may have frostbite, call your GP or 111 for advice.

If the symptoms are more severe or there are signs of hypothermia, such as constant shivering or fast breathing (hyperventilation), go immediately to your nearest A&E

A doctor will examine the affected area, check your vital signs, and ask how you got frostbite.

You may need a follow-up appointment or referral to a specialist, as the full extent of a frostbite injury often isn't apparent until a few days later.

Treating frostbite

A person with frostbite should be taken to a warm environment as soon as possible. This is to limit the effects of the injury and because it's also likely they'll have hypothermia. Don't put pressure on the affected area.

The frostbitten area should be warmed up by a healthcare professional. This is usually done by immersing the affected area in warm - but not hot - water. 

A bath of water at 37C to 39C (96.8F to 102.2F) is recommended for rewarming. The rewarming process is often painful, and regular strong painkillers may be needed.

It's important not to rewarm the affected area if there's a chance of it freezing again, as this can lead to further tissue damage.

If frostbite is severe, the loss of blood supply to the tissue may cause it to die (gangrene). A type of surgery called debridement may be needed to remove the dead tissue. Amputation may be needed if frostbite is severe.

What causes frostbite?

The body responds to cold temperatures by narrowing the blood vessels. Blood flow to the extremities slows down so flow to the vital organs can be increased.

As the blood is redirected away from the extremities, these parts of the body get colder, and fluid in the tissue can freeze into ice crystals.

The ice crystals can cause severe cell and tissue damage in the affected area. The low blood flow also deprives the tissues of oxygen. If blood flow can't be restored, the tissue will eventually die.

At-risk groups

Certain groups of people are at greater risk of getting frostbite.

They include:

• people who take part in winter and high-altitude sports, such as mountaineers and skiers
• anyone stranded in extreme cold weather conditions
• anyone who works outdoors in harsh conditions for long periods of 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 medication that constricts the blood vessels, including beta blockers (smoking can also constrict the blood vessels)

People who've taken drugs or drunk alcohol are also vulnerable to frostbite. Taking drugs or being drunk can lead to risky behaviour, not responding normally to cold, or falling asleep outside in cold weather.

As you'd expect, cases of frostbite in Wales often rise during particularly cold winters

Preventing frostbite

Most of the time frostbite can be prevented by taking precautions during cold weather.

Avoid unnecessary exposure to cold temperatures. The combination of wind and cold temperatures (wind chill) can also cause a rapid drop in temperature, so avoid going out when it's cold and windy, if possible.

It's also important to know what the early symptoms of frostbite are, particularly the tingling sensation of frostnip.

Wear appropriate clothing that protects your extremities, such as:

• well-insulated boots and a thick pair of well-fitting socks
• mittens – they provide better protection against very cold weather than gloves
• a warm, weatherproof hat that covers your ears – it's important to protect your head from the cold
• multiple thin layers of warm, loose-fitting clothing – these act as insulation

You should also try to keep dry and remove any wet clothing as soon as you can.

If you're travelling during cold weather, plan for emergencies. For example, if you're driving in icy conditions, make sure you keep a warm blanket and some spare clothes in the boot of your car in case you break down.

If you're travelling by foot, always let others know where you're going and what time you'll be back. Take a fully charged mobile phone with you so you can call for help if you have an accident, such as a fall.

Be careful when drinking alcohol during very cold weather. Drinking too much increases your risk of falling asleep in the cold, a common cause of frostbite. Alcohol also causes you to lose heat at a faster rate.

Smoking also makes you more vulnerable to the effects of the cold because nicotine can narrow your blood vessels.

Complications of frostbite

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, because your body relies on white blood cells to ward off infections.

People with frostbite are at risk of bacterial wound infections, such as tetanus. More seriously, this infection can spread into the blood (sepsis), which requires treatment with antibiotics. Both conditions require hospital admission.

Symptoms

The symptoms of frostbite progress in 3 stages.

The colder the temperature and the longer the body is exposed to freezing conditions, the more advanced frostbite can become.

Early stage (frostnip)

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

This stage of frostbite is known as frostnip, and it often affects 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 of frostbite, prolonged exposure to cold temperatures will cause more tissue damage. The affected area will feel hard and frozen.

When you're out of the cold and the tissue has 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, as 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's no lasting damage.

Advanced stage

When exposure to the cold continues, frostbite gets increasingly severe. The skin becomes white, blue or blotchy, and the tissue underneath feels hard and cold to touch.

Further damage may occur beneath the skin to tendons, muscles, nerves and bones. 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's likely that some tissue will die. This is known as tissue necrosis, and the affected tissue may have to be removed to prevent infection.

Long-term effects of frostbite

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

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 parts
• persistent pain in the affected body parts

Treatment

Treatment for frostbite depends on the severity of your symptoms. Always seek medical attention if you think you or someone else has frostbite.

If the symptoms of frostbite are minor, call your GP or 111 for advice.

If the symptoms are severe, go immediately to your nearest accident and emergency (A&E) department. If you're unable to move, call 999 to ask for an ambulance.

First aid

If medical assistance isn't available, the following steps can be taken to treat frostbite and hypothermia:

• move to a warmer place (if possible) – it's best to avoid walking on frostbitten feet and toes as it can cause further damage, but in emergency situations this may not always be possible
• gently remove gloves, boots, rings and any other items of clothing or jewellery around the affected area.
  • 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
• don't rub the affected area or apply direct heat (such as from a fire or heater) as this can cause further injury.
• don't smoke if you have frostbite (or allow someone else with frostbite to smoke) because smoking can affect blood circulation.

Rewarming the frostbitten areas

The frostbitten areas need to be rewarmed. Rewarming shouldn't be attempted until you're out of the cold.

If the warming process is started and the frozen parts are then re-exposed to the cold, it can cause further, irreversible damage.

Rewarming should ideally be carried out under medical supervision - it can be a painful process requiring painkillers and expert medical assessment. The best results are achieved using a whirlpool bath that contains a mild antiseptic.

The affected area should be rewarmed slowly by immersing it in warm (but not hot) water. A bath of water at a temperature of 37C to 39C (98.6F - 102.2F) is recommended.

Rewarming should last at least 30 minutes and should only be stopped once the affected body part is 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.

Depending on the severity of pain, strong painkillers, such as morphine, may be needed. Ibuprofen should also be taken as it has additional protective properties for frostbite.

After rewarming

After the frostbitten area has been thawed, it should be gently wrapped in clean bandages, with the fingers and toes separated. It's very important to keep the skin clean to avoid infection.

Too much movement should be avoided, and the limbs should be raised if possible. Avoid walking on affected feet and toes that have been rewarmed, as the tissues will be very delicate.

After rewarming, the skin will be discoloured and blistered, and 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 6 months.

Severe frostbite

If you have severe frostbite, you'll need to be admitted to a specialist unit where medical staff have experience in treating these types of injuries.

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

If there's a high risk of major damage, you may have thrombolytic therapy (tPA). Medicine to help break up small clots in the frostbitten blood vessels will be given as injections or through a drip in your arm.

This should improve blood flow to the affected body part, which can stimulate healing and prevent further damage. You may also be given antibiotics to prevent the affected body part becoming infected.

Iloprost is sometimes used to treat severe frostbite. It works by widening the blood vessels that supply blood to the affected body part.

When severe frostbite threatens the loss of a limb, finger or toe, a person should be considered for treatment with tPA or iloprost within 24 hours of the injury happening.

Experience has shown that treatment given within this timeframe has the best outcomes in terms of saving the affected body part.

But giving these treatments after 24 hours could still be considered to be an option at an experienced unit.

If some of the tissue of the affected body part has died (gangrene), it will need to be removed. The procedure to remove dead tissue is called debridement.

In the most serious cases, an entire part of the body, such as the fingers or toes, may need to be removed (amputated).

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

Long-term effects of frostbite

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

Unfortunately, not much can be done to treat sensitivity to cold, numbness or stiffness. A medication called amitriptyline can sometimes be effective at controlling the pain associated with the long-term effects of frostbite.