Bronchial asthma can occur at any age, but 50% of patients develop it at an early age. 20% of patients have a family history. 1.Some allergic people inhale allergens, such as pollen, acaric mites, fungal spores, etc.; eat fish, shrimp, mealybug, milk, eggs; contact with certain drugs, such as penicillin and other drugs. 2.Respiratory tract infection, cold air, irritating gas, mental tension, etc. can cause asthma attacks. 3.Occupational exposure to animal and plant or chemical dust such as cotton wool, cereals, mushroom dust, animal fur, pesticides, plastics, paints, chemical materials, etc. can cause. 4, drugs cause asthma attacks, seen in aspirin, bacterial vaccines, anti-toxic serum, insulin, etc. 5, post-exercise asthma is mostly seen in children and young people, 2 to 5 minutes after the cessation of strenuous exercise, the occurrence of asthma lasting tens of minutes to more than 1 hour. The reason may be related to the inhalation of cold air, or too much carbon dioxide exhaled from the body after exercise, caused by the relative lack of oxygen. 6.Some people have asthma attacks related to emotions and sudden onset and stop by conditioned reflex. There are also some patients who can never find out the cause of asthma.