Coughs are usually divided into three categories according to their duration: acute cough, subacute cough and chronic cough. Acute cough lasts <3 weeks, subacute cough 3-8 weeks, while chronic cough lasts ≥8 weeks. Chronic cough has many causes, and different causes have different clinical features and corresponding treatments, so it is important to clarify the cause of the cough. Common causes of chronic cough include cough variant asthma, postnasal drip syndrome, eosinophilic bronchitis, gastro-oesophageal reflux cough, endobronchial tuberculosis and post-cold cough, which account for 70%-95% of the proportion of chronic cough in respiratory medicine outpatient clinics. Asthma accounts for 24% of the single causes of chronic cough, while 28% of asthma patients have cough as the only clinical symptom. In children, cough variant asthma accounts for a higher proportion of chronic cough. Foreign studies have shown that 75% of children with chronic cough have cough variant asthma, while 54% of children with cough variant asthma may develop classic asthma. The diagnosis of cough variant asthma currently relies on the patient's cough characteristics, such as a chronic irritating dry cough with nighttime aggravation or cold, cold air, dust, and fumes that tend to trigger or aggravate the cough, no abnormal findings on chest X-ray or CT, and of course, other causes of chronic cough should be excluded. For these patients, a bronchial excitation test or PEF diurnal variability test can be performed in hospitals that have the conditions. If the bronchial excitation test is positive or the PEF diurnal variability is >20%, the diagnosis of cough variant asthma can be made. If there is no condition for bronchial excitation test, it can also be diagnostically treated with inhaled glucocorticoids plus inhaled or oral bronchodilators, and if the cough improves significantly, it can be clinically diagnosed as cough variant asthma.