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Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z



Frostbite

What is frostbite?

Frostbite is a condition where the skin and underlying tissue actually freeze. It occurs when body parts, usually the extremities such as the toes, feet, fingers, ears, nose and cheeks are exposed to extremely cold conditions. The condition rarely occurs in fit and healthy individuals in still air temperature above minus 10 degrees Celsius but may do so at higher temperatures in high winds due to the wind chill effect.

What causes frostbite?

Certain processes taking place in the body, in response to exposure to extreme cold, cause frostbite.

Who gets frostbite?

Certain groups of people are at greater risk of getting frostbite than others, these include:

What are the signs and symptoms?

The signs and symptoms of frostbite include coldness, firmness, stinging, burning, numbness, clumsiness, pain, throbbing, excessive sweating, pallor or blue skin discolouration, rotting skin and gangrene. Frostbite has been classified under the following categories that relate to the degree of injury.

First-degree frostbite

This is also called frost nip and occurs in people who live in very cold climates or do a lot of outdoor activity in winter. It involves the top layer of skin (epidermis) and presents as numbed skin that has turned white in colour. The skin may feel stiff to touch, but the tissue underneath is still warm and soft. Blistering, infection or scarring seldom occurs if frost nip is treated promptly.

Second-degree frostbite

This is superficial frostbite and presents as white or blue skin that feels hard and frozen. Blisters usually form within 24 hours of injury and are filled with clear or milky fluid. The tissue underneath is still intact but medical treatment is required to prevent further damage.

Third-degree frostbite

Deep frostbite appears as white, blotchy and/or blue skin. The underlying skin tissue is damaged and feels hard and cold to touch. Blood-filled blisters form black thick scabs over a matter of weeks. Proper medical treatment by personnel trained to deal with severe frostbite is required to help prevent severe or permanent injury. Amputation may be required to prevent severe infection.

Fourth-degree frostbite is where full-thickness damage affects muscles, tendons, and bone, with resultant tissue loss.

What treatment is available?

Prior to reaching a place that can provide proper medical attention the following should take place.

Once the patient has reached an appropriate facility the rewarming process can take place. Rewarming should be rapid to avoid further damage.

Within days of the thawing process further blisters may form. These should settle after about a week but may leave behind dead blackened tissue that form scabs. If the frostbite is superficial, pink new skin will appear beneath the scab. If frostbite is deep, the end of the finger or toe will gradually separate off. In some cases surgery may be required to remove dead tissue. This is not usually performed until 3-4 weeks after the initial injury, as the full extent of damage to tissues is not usually complete until this time.

Related information

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Author: Vanessa Ngan, staff writer

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If you have any concerns with your skin or its treatment, see a dermatologist for advice.