Frostbite is one of the serious problems that can occur with exposure to the cold. Arctic explorers and mountaineers are well known to be at risk, but others may be too.

Risk factors

It goes without saying that cold weather and being outdoors put people at particular risk of frostbite. At particular risk are the young and elderly, whose body temperature control systems may not be as well developed or reliable.

Those with blood vessel damage caused by medical conditions, such as diabetes, or because of poor lifestyle habits such as smoking and high-fat diets may also suffer frostbite more easily than others.

Drinking alcohol, smoking and taking certain medicines, such as beta blockers, increase the likelihood of frostbite when exposed to the cold.

What happens

Frostbite can happen very quickly - within minutes - at any temperature below 0°C (32°F). The lower the temperature, the quicker the damage occurs.

Windy conditions increase the risk of frostbite too.

The fluid in skin cells and the tissues beneath the skin freezes, causing damage to blood vessels and blood clots to form. This prevents oxygen from getting to the tissues. All cells need oxygen to function properly, and without it they die.

It's the extremities - the fingers, toes, face, ears and nose - that are affected most often.

Initially, the affected patches of skin become cold and white. They may tingle too, and this is called frost nip. Following this, as the damage becomes more severe, numbness develops together with blistering and pain.

Without treatment, the skin takes on a waxy feel and appears dark blue or black as the cells die. This death of the tissue is called gangrene.

Prevention

It's important to be aware that frostbite may occur and to take measures to ensure that the skin is protected.

The extremities need protecting, as these areas are usually the first to be affected and are often forgotten about.

Always wear suitably warm clothes that keep the extremities covered when outdoors. If someone is travelling to cold climates and isn't sure what clothing may be needed, it's a good idea to take professional advice.

Treatment

When frostbite is suspected, the affected areas need to be warmed. This is provided there's no risk of the areas freezing again, which could cause further and possibly irreversible damage.

Ideally, warming should be performed under medical supervision, but this isn't always possible.

It needs to be done slowly by immersing the areas in warm - not hot - water. As the areas return to a normal colour, they may appear red and swollen. Once this happens they can be removed from the water.

Never warm affected skin with direct heat, such as fire, because the lack of sensation in the skin may mean it burns.

In addition to warming, the affected areas need to be protected from further damage and infection. This can be achieved by applying a sterile dressing loosely to the skin.

Physiotherapy can help to improve circulation to the frostbitten area. Sometimes, however, the damage can't be repaired and to prevent further damage to surrounding healthy skin amputation of the dead areas is needed.

Frostbitten areas usually recover within six months, but people who have been affected may be left with permanent problems such as pain, stiffness and numbness.

This article was last medically reviewed by Dr Trisha Macnair in January 2008