The causes of asthma are complex and varied, and can be broadly divided into two categories: (1) External causes: (1) Infections: Infants and children are common. Various pathogenic microorganisms can cause or induce asthma, among which viruses such as respiratory syncytial virus and mycoplasma and chlamydia infections are common, while bacterial infections are rare. (2) Allergens: a. Airborne pollen, mold, dust, cat, dog and bird dander, lint, mite excrement and old lint, sofas, carpets, toys and bedding, etc. b, food allergens, including milk, eggs, meat, fish, shrimp, peanuts, sesame, flour, corn and various nuts, vegetables, fruits, etc. c, drugs: such as aspirin, penicillin, sulfonamides, etc. d, various physical and chemical factors: such as cold air, automobile exhaust, paints, insecticides, cosmetics, preservatives, flavorings, etc. It should be especially noted that in some children too sweet or salty food can also trigger asthma. (3) Climate and environment: seasonal changes, temperature changes, high humidity and air pollution, etc. (4) Exercise: Exercise can also trigger asthma or wheezing cough. (2) External causes: (1) Genetic: In some patients, there is a clear correlation. Most children with asthma have allergies, which are also associated with heredity. (2) Immune dysregulation: It can make the organism allergic reaction enhanced and anti-infection ability decreased, which makes it easy to have allergic reaction and respiratory tract infection, thus making asthma recurrent. (3) Mental and neurological factors: strong mental stimulation, drastic emotional changes, panic, tension, fatigue and excessive stress can trigger asthma. (4) Other: trace elements, vitamin deficiency, etc. may also have some relationship.