Why do my hands get cold when the weather is cold?

Humans are warm-blooded animals, and the billions of cells in the human body can only survive at a constant temperature, that is, around 37°C. As the external temperature continues to change, the human body uses the brain's thermoregulatory center to regulate the body's heat production and heat dissipation to maintain a constant body temperature. In winter, when the temperature drops below 10°C, the blood vessels in the exposed parts of the human skin will shrink. If the arteries shrink for a long time, the circulation will slow down, and the veins will store too much blood, and the nutrients that should be supplied by fresh blood will be lacking, which will cause The skin and subcutaneous tissue are damaged, resulting in frostbite or local necrosis. When the environment is humid, the clothes on your body are damp, or your body is sweating, the moisture itself will absorb part of the heat, so being cold and wet is more likely to cause frostbite. The hands and feet of the human body are far away from the heart and are located at the end of blood circulation. They have less blood supply and are more exposed. Therefore, the hands will freeze when the weather is cold. And because the weather is cold and the blood does not circulate, it is easy to get chilblains. But when the weather warms up, the blood naturally circulates again, and the chilblains disappear, so it will be very itchy when the weather is warm.