Urticaria is a limited edematous reaction due to reactive dilation and increased permeability of small blood vessels in the skin and mucous membranes. Most patients cannot find the exact cause, especially chronic urticaria. The common causes of urticaria are as follows: 1. Food Mainly animal proteins such as fish, shrimp, crab, shellfish, meat, milk, eggs, etc. and plants such as mushrooms, strawberries, cocoa, tomatoes and onions and garlic, etc. Food additives can also cause allergies such as salicylic acid, citric acid, benzoin, sulfites, etc. Some of these substances can be used as allergic reactions. Some of these substances can be used as allergens to cause hypersensitivity reactions, while others can directly stimulate the release of histamine from mast cells. 2, drugs Many drugs can cause the disease by causing hypersensitivity reactions in the body common such as penicillin, serum preparations, various vaccines, furazolidone and sulfonamide. And some drugs are histamine releasing substances, such as aspirin, morphine, codeine, quinine, hydrazinepyridazine, atropine, trichothecene, poppy bases, etc. 3, infections Various viral infections such as viral upper respiratory tract infection, hepatitis, infectious mononucleosis and coxsackievirus infection, bacterial infections such as sepsis caused by Staphylococcus aureus and streptococcal infection, tonsillitis, chronic otitis media, sinusitis, Helicobacter pylori infection, fungal infections such as superficial and deep fungal infections and parasitic infections such as Ascaris lumbricoides, hookworm, Plasmodium vivax, Schistosoma haematobium, pinworms, filarial parasites, etc. Schistosomes, pinworms, filarial worms and lyso-amoeba can cause urticaria. Physical factors such as cold, heat, light, friction and pressure can cause the onset of urticaria in some patients. 5, animal and plant factors such as animal fur, insect toxins, snake venom, jellyfish toxins, Xunma and pollen, etc. 6, mental factors mental stress can cause the disease by causing the release of acetylcholine. 7, visceral and systemic diseases such as rheumatic fever, rheumatoid arthritis, systemic lupus erythematosus, malignant tumors, band disorders, endocrine disorders, autoimmune thyroiditis, etc. can become the cause of urticaria, especially chronic urticaria. 8, other factors Inhalants such as house dust, aerosols, volatile chemicals, pregnancy or menstrual cycle can trigger the disease.