Frostbite is an injury caused by freezing of the skin and underlying tissues. The early stage of frostbite is called frostnip. It causes a cold feeling followed by numbness. As frostbite gets worse, the affected skin may change color and become hard or waxy-looking.

Exposed skin is at risk of frostbite in conditions that are freezing cold and windy or wet. Frostbite also can occur on skin covered by gloves or other clothing.

Mild frostbite gets better with rewarming. Seek medical attention for anything more serious than mild frostbite because the condition can cause permanent damage to skin, muscle, bone and other tissue.

The most common cause of frostbite is exposure to freezing cold. The risk rises if the weather also is wet and windy. Frostbite also can be caused by direct contact with ice, freezing metals or very cold liquids.

Risk factors for frostbite include:

• Being in freezing conditions without protective clothing.
• Having certain medical conditions, such as diabetes, exhaustion, poor blood flow or congestive heart failure.
• Regularly smoking tobacco.
• Having impaired judgment while in very cold conditions.
• Having had frostbite or another cold injury in the past.
• Being an infant or older adult in cold conditions. People in these age groups have a harder time producing and retaining body heat.
• Being in cold conditions at high altitude.

Complications of frostbite include:

• Hypothermia.
• Increased sensitivity to cold and a higher risk of frostbite in the future.
• Long-term numbness in the affected area.
• Excessive sweating, also called hyperhidrosis.
• Changes in or loss of nails.
• Growth problems in children if frostbite damages a bone's growth plate.
• Infection.
• Tetanus.
• Gangrene, which can result in having the affected area removed. This procedure is called amputation.

Frostbite can be prevented. Here are tips to help you stay safe and warm.

• Limit time outdoors when it's freezing cold and wet or windy. Pay attention to weather forecasts and wind chill readings. The risk of frostbite increases the longer you're in freezing conditions. And frostbite can happen in an instant if bare skin touches something cold, such as freezing metal.
• Dress in loose layers. Air trapped between the layers helps insulate you from the cold. Choose undergarments that wick moisture away from the skin. Next put on something made of fleece or wool. For the outer layer, wear something windproof and waterproof. Change out of wet gloves, hats and socks as soon as possible.
• Wear a hat or headband made for cold weather. Make sure it covers your ears.
• Wear mittens. Mittens provide better protection than do gloves. Under a pair of heavy mittens, also wear glove liners, which wick moisture away from the skin.
• Wear socks and sock liners. Make sure they fit well, wick moisture and provide insulation.
• Watch for symptoms of frostbite. Early signs of frostbite are slight changes in skin color, prickling and numbness. Seek warm shelter if you notice symptoms of frostbite.
• Plan to protect yourself. When traveling in cold weather, carry emergency supplies and warm clothing in case you become stranded. If you'll be in remote territory, tell others your route and expected return date.
• Don't drink alcohol if you plan to be outdoors in cold weather. Alcoholic beverages cause the body to lose heat faster and can impair judgment.
• Eat well-balanced meals and stay hydrated. Doing this even before you go out in the cold helps you stay warm.
• Keep moving. Exercise can get your blood flowing and help you stay warm, but don't do it to the point of exhaustion.

Diagnosing frostbite is based on your symptoms and a review of recent activities during which you were exposed to cold.

Your healthcare team may have you undergo X-rays or an MRI to look for bone or muscle damage. It may take 2 to 4 days after rewarming to tell the extent of tissue damage.

First aid for frostbite is as follows:

• If you suspect hypothermia, call for emergency help.
• Protect the injured area from further damage. Do not try to rewarm the frostbitten skin if it might freeze again.
• Get out of the cold, remove wet clothes and wrap up in a warm blanket.

• If possible, soak the skin with frostbite in a tub or sink of warm water for about 30 minutes. For frostbite on the nose or ears, cover the area with warm, wet cloths for about 30 minutes.

  Another option is to warm the affected skin with body heat. For example, tuck frostbitten fingers under an armpit.

• Don't walk on frostbitten feet or toes if possible.
• Take a nonprescription pain reliever if needed.
• Drink a warm, nonalcoholic beverage.
• Remove rings or other tight items. Do this before the injured area swells with rewarming.
• Don't apply direct heat. For example, don't warm the skin with a heating pad, a heat lamp, a blow-dryer or a car heater.
• Don't rub the frostbitten skin.

After providing first aid, seek treatment from a healthcare professional if you have frostbite. Treatment may involve rewarming, medicine, wound care, surgery or other steps depending on how serious the injury is.

• Rewarm the skin. If the skin hasn't been rewarmed already, your healthcare team rewarms the area using a warm-water bath for 15 to 30 minutes. The skin may turn soft. You may be asked to gently move the affected area as it rewarms.
• Take pain medicine. Because the rewarming process can be painful, you may be given a pain reliever.
• Protect the injury. Once the skin thaws, your healthcare team may loosely wrap the area with sterile sheets, towels or dressings to protect the skin. You may need to raise the affected area to reduce swelling.
• Soak in a whirlpool. Soaking in a whirlpool bath can aid healing, as it keeps the skin clean and naturally removes dead tissue.
• Take infection-fighting drugs. If the skin or blisters look infected, your healthcare team may prescribe antibiotic medicine taken by mouth.

• Take medicine. You may receive an injection of medicine in a vein that helps restore blood flow. This type of medicine is called a thrombolytic. One example is tissue plasminogen activator, also called TPA. Studies of people with severe frostbite show that TPA may lower the risk of amputation. But this medicine can cause serious bleeding. It's sometimes used in serious situations and within 24 hours of cold exposure.

  Another medicine that improves blood flow is iloprost (Aurlumyn). It was recently approved by the FDA for severe frostbite in adults. It can reduce the risk of finger or toe amputation. Side effects of this medicine include headache, flushing and heart palpitations.

• Remove damaged tissue. To heal properly, frostbitten skin needs to be free of damaged, dead or infected tissue. This procedure to remove this tissue is called debridement.
• Tend to blisters and wounds. Blisters can act as a natural dressing. Depending on the type of blisters, your healthcare team may leave them to heal on their own or drain them. A variety of wound care techniques may be used depending on the extent of injury.
• Undergo surgery. People who have experienced severe frostbite may in time need surgery or amputation to remove dead or decaying tissue.

After rewarming, your skin may stop tingling and return to its usual color within a few hours. Deep tissue injury may heal slowly and be very sensitive to the touch for weeks. Take all medicines as prescribed by your healthcare team. For mild frostbite, a nonprescription pain reliever can help ease symptoms.

Seek medical care if you suspect you have frostbite. For serious frostbite, you may be told to go to an emergency room.

If you have time before your appointment, use the information below to get ready.

What you can do

• List any symptoms you have and how long you've had them. It helps your healthcare team to have as many details as possible about your cold exposure and to know if your symptoms have changed.
• List your key medical information, including any other conditions with which you've been diagnosed. Also list all medicines you're taking, including nonprescription medicines and supplements.
• Make a note of the date of your last tetanus shot. Frostbite increases the risk of tetanus. If you haven't had a tetanus shot or haven't had one within five years, your healthcare team may recommend that you get a shot.
• List questions to ask your healthcare team. Being prepared helps you make the most of the time you have with your healthcare team.

For frostbite, some basic questions to ask your healthcare team include:

• Are tests needed to confirm the diagnosis?
• What are my treatment options and the pros and cons for each?
• What results can I expect?
• What skin care routines do you recommend while the frostbite heals?
• What kind of follow-up, if any, should I expect?
• What changes in my skin should I look for?

Don't hesitate to ask any other questions that occur to you.