How does chronic urticaria cause

Chronic urticaria is a wheal attack or intermittent attack lasting more than 6 weeks. The cause of it is not very clear. First, it may be due to some physical factors, such as hot and cold stimulation, friction, stress, sunlight exposure, food, such as animal protein, vegetables, fruits, etc., in addition to some rotten food and food additives, etc. Some patients may also be due to drugs, implants, chronic diseases, infections, fatigue, and mental stress. The cause of chronic urticaria is difficult to define.