When temperatures drop as winter settles in, parents around the world urge their children with stern warnings to bundle up like a mummy to ward off the effects of the cold.

What's the worst that can happen if they don't listen? They get a little cold, right? Wrong! If they get frostbite, they'll wish they had listened and dressed appropriately.

Frostbite has been around forever. A 5,000-year-old Chilean mummy offers the oldest evidence of frostbite.

Baron Dominique Larrey, a surgeon in Napoleon's army, first described frostbite medically in 1812, during the French army's retreat from Moscow.

Frostbite (or congelatio in medical terminology) occurs when skin and other tissues freeze due to extreme cold. Frostbite usually happens in parts of the body farthest from the heart, such as the nose, cheeks, ears, fingers and toes.

At or below 32° F, blood vessels close to the skin begin to constrict, pushing blood away from the extremities and closer to the heart. This is one of your body's survival techniques, as it helps to maintain core body temperature.

In situations of extreme cold or prolonged exposure, blood flow to the extremities can be reduced to dangerously low levels, leading to the freezing and death of skin tissue in affected areas. There are different degrees of frostbite.

The most minor, sometimes called "frostnip," affects only the surface of the skin and usually does not result in permanent damage. More serious degrees of frostbite result from prolonged exposure to extremely cold temperatures.

The longer the body is exposed, the greater chance there is of permanent damage to skin, muscles, blood vessels and nerves. Extreme cases of frostbite can result in severe permanent skin and nerve damage and even loss of extremities.

When you are outside in cold weather for long periods of time, be on the lookout for itching and pain, as well as white, red or yellow patches on the skin. These, along with numbness, are signs of frostnip and, potentially, frostbite.

There are many factors that contribute to frostbite, including extreme cold, wet or otherwise inadequate clothing, high winds and poor circulation. Poor circulation can result from clothing or boots that are too tight, fatigue, alcohol and tobacco use, or disease, such as diabetes.

To treat frostbite, you need to thaw the affected areas. This must be done slowly and very carefully, though. A stable, warm environment is needed, as thawing and subsequent refreezing can cause even more damage.

It's also very important to avoid rubbing or massaging affected areas. Rubbing frostbitten tissues can cause ice crystals that have formed in the tissue to do further damage.

If you suspect someone has frostbite, it's best to move him or her to a warmer area and wrap him or her in a blanket, while seeking professional medical help.

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If today’s lesson on frostbite gave you the blues, head on back to Wonderopolis tomorrow for a lesson on dynamite denim!