Urticaria is a very common allergic disease in dermatology, and its causes are very complex, and many of them cannot be fully identified, especially for chronic urticaria with a long duration (more than 6 weeks). What are the common causes of urticaria? 1. food or additives in food, such as milk, eggs, seafood, etc. 2. inhalants, including pollen, dust mites, animal fur, etc. 3. infections, including viral or bacterial infections. 4. medications, which are also a very important cause of urticaria. 5. physical factors, such as hot and cold stimuli, sunlight, mechanical stimuli, etc. 6. animal and insect bites. 7. 7. mental and nervous factors are also causes of hives. Therefore, the causes of hives are very many and complex, so we need to identify the suspected causes as much as possible, and then treat them symptomatically.