Why does my hand turn red and purple when it is cold, and normal when it is hot?

It is caused by poor blood circulation in winter.

The above situation is normal. After work, you can soak your hands in warm water and wash your hands with soap and hand sanitizer. Then, apply some hand cream on your hands, apply it gently and evenly, and massage for a while, focusing on the back of your hands and fingers. Make a fist with both hands and then extend it, and repeat it seven or eight times; The fingers are relaxed, and the forearm drives the wrist to rotate gently, from the chest to the top of the head, and then back to the chest, and do it three or four times repeatedly.