When water is heated, it doesn’t change in temperature. Similarly, when blood freezes inside the body, it does not change in temperature. The freezing point of blood is -2 degrees Celsius.
During cold weather, your body shifts blood flow from the larger extremities (your arms and legs) to the smaller extremities, like your hands and feet. This allows your skin and extremities to quickly cool down.
Your body also shifts its energy away from keeping your core (chest and abdomen) warm to regulating blood flow to the extremities, a process called vasoconstriction. This decreases the blood flow to your hands and feet and causes them to turn a blue color, which is called cyanosis.
A person’s hands and feet are especially vulnerable to frostbite. When your blood freezes in your hands and feet, ice crystals form and damage the cells that make up these tissues.
Frostbite leads to a loss of feeling and color in the affected areas, which can be painful and lead to permanent injury or death. In severe cases, frostbite can lead to amputation of the affected body part.
If you get exposed to temperatures below 35 C (95 F), your body’s internal temperature can drop to dangerously low levels called hypothermia. Symptoms of hypothermia include shivering, weakness and confusion. It can be life-threatening and requires immediate emergency medical care. The risk of hypothermia increases for infants and young children, as well as older adults.
