2. Allergic reaction: allergic to food, medicine, insect poison or other substances, such as pollen allergy or contact with allergens, mostly occur in people with allergic constitution.

3. The concentration of cholic acid is too high: when the concentration of cholic acid in blood increases, it will be deposited on the skin, causing serious skin itching. Therefore, when the skin is itchy and yellow, you should go to the hospital to check your liver and gallbladder to see if you have gallstones.