Urticaria patients do allergen test, some patients can find the cause of the disease, and some patients can not find allergens. Because the triggering cause of urticaria is very complex, a variety of causes, some are caused by foreign inhalation, some are caused by drugs, and some are caused by body parasites, bacteria, or autoantibodies, i.e., autoimmune diseases, including foreign allergens, infections, and the body’s own factors. Therefore, not all patients can be checked for the triggering factors of urticaria during allergen examination.