Urticaria is divided into acute and chronic urticaria, and chronic urticaria is divided into chronic spontaneous urticaria and chronic inducible urticaria. Chronic spontaneous urticaria has no specific trigger point and is spontaneous, while chronic inducible urticaria is divided into physical, cholinergic, contact and water urticaria depending on the triggering factor. Chronic urticaria is treated differently depending on the subtype. Therefore, it is necessary to determine the subtype of each case of chronic urticaria. I. Acute urticaria has a short course and information on the cause can often be obtained from the medical history, such as acute infections, medications or consumption of specific foods. Therefore, an etiologic diagnosis of acute urticaria is not recommended, but only if specific allergen screening is suspected to help patients avoid re-exposure to allergens. Second, chronic urticaria generally requires allergen testing. A two-step diagnostic approach is used. First, blood sedimentation (ESR) and C-reactive protein (CRP), routine blood count and white blood cell sorting count are tested to exclude diseases caused by auto-inflammatory disorders, such as urticarial vasculitis. Second, according to the patient’s medical history, tests related to self-serum allergen testing, food intolerance or chronic infections such as Helicobacter pylori are done for persistent and severe chronic spontaneous urticaria to identify the cause and provide relevant treatment.