Hives manifest as red or skin-colored bumps (which are flat bumps that float on the skin like a cloud). These bumps usually fade completely within a day and do not leave a black mark after they have faded. If the lesions are recurrent and persist for more than 6 weeks, then chronic urticaria is the first consideration. If they do not resolve within one day and leave a black mark afterwards, then urticaria-like vasculitis is considered and a pathologic biopsy is needed to confirm this. Some patients with chronic urticaria may have a combination of diseases of the visceral system, and it is recommended to check for thyroglobulin antibodies (blood test) and Helicobacter pylori in the stomach (a breath test can be performed at the hospital). If the patient has a combination of these two problems, he/she will be very slow to get well. They should be treated in the appropriate department first. Regarding allergen detection, you can stop all anti-allergy drugs and go to the allergist department or dermatology department for allergen detection when the condition is not severe and you can stop the drugs for a short time. It is recommended to use blood sampling, needle prick and patch test instead of ultrasound. Even if the allergen is found, it is only for reference and you have to look for allergens depending on what you encounter in your life or what foods you eat that cause recurrent skin lesions. If all of the above lab tests are okay, chronic urticaria should be treated with long-term anti-allergy medication that is gradually reduced. Hives vasculitis, you need to go to the hospital, the doctor prescribe special drugs to treat.