Prolonged exposure to extreme cold can damage skin and underlying tissue, known as frostbite. At fi...
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Prolonged exposure to extreme cold can damage skin and underlying tissue, known as frostbite. At first, your skin may turn red, and then white or pale as your body reduces blood flow to your extremities to maintain your core temperature and to protect vital organs, such as your heart and brain, from becoming cold and damaged. To reduce blood flow, the blood vessels close to the skin's surface narrow. To preserve blood flow and function of your hands and feet, the blood vessels alternately widen and narrow but with continued exposure, they permanently constrict. About 60 percent of your body weight is water. When skin heat drops too low, water between the skin cells forms ice crystals and is also lost from inside the cells. Both cause skin cells to die. Continued exposure also damages blood vessels so that blood flow is further impeded, small clots form and the vessels leak. Depending on the severity, frostbitten skin may turn purple or blue as it rewarms, or black and hard as tissue dies.

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