Fingernail suddenly black purple is how to return a responsibility

Causes of black and purple fingernails: 1. Insufficient blood supply to the human body will cause local hypoxia in the fingers, and the color of the fingernails will gradually deepen, so they will turn purple and black. 2. Anemia. Anemia can cause fingernails to turn purple. People with low blood will cause fingernails to turn purple. 3. The weather is too cold. If you wear too little, it will cause blood vessels to contract, and the blood circulation of the peripheral nerves will be poor, which can cause the fingernails to turn black and purple.