Frostbite happens when you are exposed to extreme cold. Most likely to get frostbite: The unprotected parts or your body and the parts of your body with less blood flow.

It usually affects your toes, nose, ears, cheeks, chin, and fingers. When you are out in the cold, your body tries to preserve heat. More blood is forced to your core to keep your heart and lungs warm. Blood flow is reduced to your extremities -- such as fingers and toes. That makes the skin and tissue more likely to freeze.

You can get frostbite very quickly, if it's cold enough. Most frostbite cases, however, happen when people are exposed to freezing temperatures for a long time. When the temperature is below zero degrees Fahrenheit (including windchill), your bare skin can freeze in five minutes. At windchill temperatures between -20 and -69 degrees, skin can freeze in a minute. And below -70, it can freeze in just 30 seconds.

Because of the wind chill factor, you could get frostbite even if the air temperature is above freezing, according to the National Weather Service. That's because windchill can bring the temperature to below freezing for people.

A good way to treat frostbite is to soak the part of the body that's affected in warm water. The temperature should be comfortable to the touch, but not hot. If you can put your uninjured hand in the water for 30 seconds, the temperature is OK. Let the frostbitten area soak for about 30 minutes, or until it gets soft and flexible. Rewarming can really hurt, and over-the-counter pain medications can help. Don't attempt to rewarm any parts of the body if there's a chance of refreezing.

Get medical help as soon as you can.

At the first sign of frostbite, get out of the cold and find medical attention. You should take off any wet or restrictive clothing, and rest and elevate the affected area. Don't touch any blisters. Drinking tea or other warm beverages also may help.

Don't walk on frostbitten toes or feet unless you absolutely have to. And don't rub or massage the affected area. That could cause more damage. If you can, soak the affected areas in warm water. Don't get close to a fire or source of dry heat. Frostbitten skin is numb and can get burned easily.

Exercise may help you avoid frostbite because it keeps the blood flowing to the parts of your body most often affected.  But exhaustion is also a risk, so don't overdo it.

In cold weather, experts say you should wear loose-fitting, layered clothing, which helps with ventilation and insulation. And wool is a better choice than cotton because it doesn't lose its ability to insulate when it gets wet.

Even better is a mix of different materials for different layers. The CDC says you should wear an inner layer of wool, silk, or polypropylene. The outer layer should be wind resistant so you don't lose body heat from the wind. A water-repellent fabric will protect you from moisture, which can chill the body very quickly.

If you are stranded in a car in the cold, you can run the engine and heater for ten minutes every hour to stay warm. Roll down one window a little bit to avoid carbon monoxide fumes. Make sure the exhaust is not blocked by snow or ice.  Tie a bright piece of cloth to your radio antenna, stay with your car, and call for help immediately.

Whatever winter activity you enjoy, make sure that someone knows where you are going and when you expect to return. Always take extra, dry clothing, food, and a first-aid kit if possible.

Fluids within frostbitten tissue actually do freeze, forming ice crystals. The freezing causes dangerous changes in your cells that can be permanent.

That's why frostbite injuries can take so long to heal. Blisters may form within days of your skin thawing out, and that can cause infection. After a week, the blisters may scab over, and dead tissue can fall off. It can take weeks or even months before you know whether any tissue is permanently damaged.

Most frostbite injuries get better with the right treatment. Sometimes, amputation is necessary, but that's only in the most extreme cases.

The seriousness of frostbite ranges all the way from superficial to deep. With surface injuries, you will have some swelling, redness, and blisters, but no permanent damage. Deep frostbite affects muscles, tendons, and bones, and can lead to amputation.

Both frostbite and hypothermia can be caused by cold temperatures. But frostbite happens when certain parts of the body are injured from being too cold. Hypothermia is when your overall body temperature is too low.

Hypothermia can be life-threatening. You should seek medical care as soon as possible with either hypothermia or frostbite.

Anything that limits the flow of blood to your skin or your hands, feet, nose, or ears can increase your risk for frostbite. This includes heart disease, poor circulation, diabetes, and dehydration. Some medications also can raise your risk, such as beta-blockers, which are used to control the symptoms of heart failure, prevent migraine headaches, and treat certain kinds of tremors. Drugs, alcohol, and nicotine can also reduce the flow of blood to the skin. And alcohol can cloud your judgment, which raises your risk even more.

When it's freezing outside, metal jewelry can speed up the cooling of your skin and your risk of frostbite. Ears are one of the most often frostbitten parts of the body, so earrings are especially risky. Make sure you keep your ears covered.

If there's a chance of refreezing, you shouldn't try to rewarm any parts of the body that might be frostbitten. For example, if a person with frostbite is out in the wilderness and will have to travel through more cold weather to get help. That's because frostbitten tissue can be very delicate. If the injury is thawed and then refrozen, there's a greater chance for gangrene, loss of tissue, or even amputation.

Children are more likely to get frostbite because they lose heat from their skin faster than adults. They're also more likely to stay outside too long even though it's very cold.

You should dress children in layered, loose-fitting clothes.  And don't forget insulated boots, hats, and gloves or mittens.

Just because an animal is covered in fur doesn't mean it can't get frostbite.  When temperatures drop below freezing, dogs, cats, and other pets are at risk. And the early signs of frostbite can be hidden under all that fur.  Ears, toes, tails, stomach, and faces are most affected. Frostbitten skin may get pale, white, blue, or gray, and can be unusually cold to the touch.

If you think your pet has frostbite, call a veterinarian right away.

Chilblains are sometimes thought of as mild frostbite. Actually, they're a different kind of cold injury, but are brought on by non-freezing temperatures. Chilblains, also called Pernio or Perniosis, are caused when your skin is exposed to temperatures just above freezing over and over again.

Some symptoms are similar to early frostbite, including redness and blistering. But chilblains also cause itching and inflammation.