The causes of chronic urticaria are complex and difficult to define, and are categorized into exogenous and endogenous based on different sources, such as physical factors, drugs, food, chronic infections, and so on. 1. Exogenous factors: (1) Common exogenous factors are physical factors such as pressure, heat and cold, friction, sunlight exposure. (2) Food factors, such as fruit mango, animal protein fish, shrimp and eggs, alcohol, food additives. (3) Drug factors, such as sulfonamides, various vaccines, penicillin, codeine, aspirin and so on. (4) Implants such as heart valves, artificial joints, orthopedic steel nails, etc. These may cause chronic urticaria. 2. Endogenous factors: endogenous factors often act continuously, and common causes include chronic insidious infections such as viral, bacterial, fungal and parasitic infections, as well as fatigue, vitamin D deficiency or stress, and certain systemic diseases such as rheumatic fever, systemic lupus erythematosus, and thyroid diseases. Suspected chronic urticaria, you need to check and clarify in time, and follow the doctor’s instructions to standardize the treatment, so as not to delay the condition.