Asthma triggering factors in children can be divided into two categories, one is the factors that cause bronchial smooth muscle spasm and the other is the factors that cause airway hyperresponsiveness with delayed inflammatory response. 1, the factors of bronchial smooth muscle spasm (1) climate change: climate change is very sensitive to children, such as sudden cold, stimulated by cold air or reduced air pressure, often can trigger an asthma attack. Therefore, the onset of asthma in children is more common in the cold season, which is also related to respiratory tract infections. (2) Exercise: When children exercise vigorously, it can cause asthma attacks. Exercise-induced asthma attack is due to the exhalation and loss of a large amount of water from the alveoli through the airways in a short period of time, and under physical stimulation, many cells produce and release mediators that cause smooth muscle contraction, while nerve conduction may be involved, resulting in reflex bronchospasm and asthma. (3) Non-specific physicochemical factors: On the basis of increased airway reactivity in children with asthma, certain non-antigenic substances, such as mosquito incense, cigarette smoke, vegetable oil, gasoline and paint odor, can stimulate the sensory nerve endings under the bronchial mucosa, reflexively causing coughing and stimulating the vagus nerve and producing bronchial smooth muscle spasm. 2. Factors of airway hyperresponsiveness with delayed reaction (1) Infection: Respiratory tract infection, especially respiratory viral infection, is the main cause of asthma triggering in children. In recent years, most studies have shown that viruses predominate in respiratory infections and bacterial infections do not play a major role either in asthma attacks or in secondary infections of bronchial asthma. There are different pathogens for different ages. Preschool children are often infected with rhinovirus, Mycoplasma pneumoniae, parainfluenza virus, and respiratory syncytial virus. (2) Proto-mite: Children are more allergic to mites than adults, and most attacks occur at night. Allergy to mites causing asthma is characterized by early onset of the disease. In a survey of 143 children with asthma, 61.5% had their first asthma attack within 3 years of age, indicating that such infantile asthma can be allergic or will later turn into allergic asthma. (3) Other factors: non-pathogenic bacteria (Streptococcus A, Neisseria), fungi, milk, poultry eggs, pollen, cotton wool, silk, animal hair, feathers, moths, malaria parasites and emotional changes (such as crying and laughing, nervousness and fear) can cause the onset of asthma in some children.