Prolonged exposure to cold weather or brief exposure to extreme cold temperatures can result in a cold injury. Cold injury affecting the body's shell is called frostbite, while cold injury involving the body's core is known as hypothermia.

It is possible to suffer each of these separately, although they often occur simultaneously. The body's response to cold temperature is to constrict blood vessels, limiting blood flow to extremities, especially the fingers and toes, along with the release of hormones that cause shivering to increase heat production.

Frostbite

Frostbite happens when tissues freeze after exposure to temperatures below the freezing point of skin, commonly affecting the nose, cheeks, ears, fingers, and toes. Frostbite may be either superficial or deep. Symptoms of superficial frostbite include burning, numbness, tingling, itching, or cold sensations and the affected areas appear white and frozen, but if pressed on retain some resistance.

Symptoms of deep frostbite include first a decrease and then a complete loss in sensation. Other symptoms include swelling, blood-filled blisters, and white or yellowish skin that appears waxy and will turn a purplish blue when rewarmed. The area will become hard with no resistance when pressed on, sometimes looking blackened and dead.

Deep frostbite causes considerable pain when the blood flow is re-established and the area is rewarmed followed by a dull continuous ache and throbbing sensation in the first two to three days and lasting for weeks to months as healthy tissue separates from dead tissue.

First Aid for Frostbite

For any signs of frostbite, take the following steps:

• Get out of the cold if you can and call for help while keeping the affected part elevated.

• Remove jewelry and clothes that may be blocking blood flow and begin to hydrate with nonalcoholic, noncaffeinated fluids.

• Apply a dry, sterile dressing and separate frostbitten fingers or toes with cotton, and get to a medical facility as quickly as possible.

• Never attempt to rewarm a frostbitten area because it may freeze again and the thaw-refreeze cycle is extremely harmful.

• Don't rub the frozen area with snow or anything else as rubbing causes further tissue damage (the amount of tissue damage is directly related to the time frozen, not to the degree of temperature).

Hypothermia

When you are exposed to cold temperatures or to cool, damp environments for prolonged periods, your body's control mechanisms may not be able to keep your body temperature normal and hypothermia can result. Hypothermia happens when your internal body temperature is less than 95°F, with gradual symptoms such as shivering, slurred speech, slow breathing, cold, pale skin, loss of coordination, fatigue, lethargy, or apathy. Children and elderly people have a higher risk of developing hypothermia.

First Aid for Hypothermia

Follow these steps for first-aid treatment of hypothermia:

• Call 911 and monitor the person's airway, breathing, and circulation while waiting for help to arrive.

• If you are able to, move the person out of the cold, and at the very least, attempt to protect the person from the wind and from the cold ground.

• Remove all of the person's wet clothing and cover them with a warm, dry covering. Never apply direct heat like a hot-water bottle or heating pad; use warm packs applied to the neck, chest wall, and groin. Avoid attempting to warm the arms and legs, because the heat will force cold blood back to the heart, lungs, and brain, causing a drop in the core body temperature that can be fatal.

• If the person is not vomiting, give them warm, nonalcoholic drinks. Handle the person gently, don't massage or rub them because a person with hypothermia is at risk of cardiac arrest.