5 things you need to know about frostbite

Thanks to well-designed clothes and sports equipment, frostbite may not be as common as in years gone by, but it's still a very real winter threat. "We now have whatever we need not to be stuck inside during the winter," says Dr. Pierre Frémont, a professor of rehabilitation at Université Laval in Quebec City. "So go outside and enjoy, but be aware of the weather and be equipped." Here's what you need to know about frostbite.

1. The risk of frostbite begins at about -10 C.
When temperatures drop this low and there is a wind, the risk of frostbite becomes very real. "Remember, if you're skiing downhill, you're creating wind," says Frémont. And the windchill factor you're creating can be considerable. At -20 to -25 C, frostbite can occur within minutes, he says, even in the absence of wind.
Click here to see the risk according to temperature.

2. The deeper the "injury" the more severe the frostbite.
A first-degree cold injury (called frostnip) involves only the outer layers of the skin, turning it white and leaving it numb. It's only when deeper layers of skin and tissue are affected that you have frostbite. That happens when blood vessels constrict to prevent heat loss and crystals form inside tissue. In second-degree frostbite, skin is white or blue and feels frozen but the tissue underneath is not yet damaged. Third-degree frostbite describes white, blotchy or blue skin with underlying tissue damage.