Chronic cough has many causes and can usually be divided into two categories: (1) Those with definite lesions on initial chest X-ray, such as pneumonia, tuberculosis, bronchopulmonary cancer, etc. (2) Those with no obvious abnormalities on chest X-ray and cough as the main or only symptom, which is usually referred to as chronic cough of unknown origin (chronic cough for short). Common chronic coughs (1) Chronic irritant cough Mostly sensitive to fumes, dust, odors or cold air, without symptoms such as shortness of breath or dyspnea, with no abnormalities on physical examination, normal pulmonary ventilation function and peak flow rate variability, and no evidence of airway hyperresponsiveness. (2) Gastroesophageal reflux chronic cough with predominantly daytime cough, 24-hour esophageal PH monitoring DeMeester score greater than or equal to 12.70 and/or symptom correlation probability greater than or equal to 75%, exclusion of cough variant asthma, postnasal drip syndrome and eosinophilic bronchitis, and significant disappearance or reduction of cough after anti-reflux treatment. Treatment: Lifestyle modification: weight loss, eating less and more meals and smoking cessation. High pillow position and elevation of the head of the bed. Application of acid suppressants, gastrointestinal stimulants such as domperidone, etc. If there is underlying gastroduodenal disease with H. pylori infection, the appropriate treatment should be considered. (3) Allergic cough Some chronic coughs have some specific factors and are effectively treated with antihistamines and glucocorticoids, but cannot be diagnosed as asthma, allergic rhinitis or eosinophilic bronchitis, defining this type of cough as allergic cough. Its relationship with allergic pharyngitis, eosinophilic bronchitis, and post-cold cough needs to be further clarified. (4) Post-cold cough When the cough persists even after the symptoms of the acute phase of the cold itself have disappeared, it is clinically called post-cold cough. It can last for 3-8 weeks or even longer, but it is often self-limiting, usually relieving on its own, with no abnormalities on X-ray chest examination and ineffective antibacterial drug treatment. For some chronic prolonged coughs, central sedatives and antihistamine H1 receptor antagonists can be applied for a short time. (5) Angiotensin-converting enzyme inhibitor (ACEI)-induced cough Cough is a common adverse effect of taking ACEI-type antihypertensive drugs, with an incidence of 10%-30%, accounting for 1-3% of the causes of chronic cough. Cough relief after discontinuation of ACEI can confirm the diagnosis. The cough usually disappears or is significantly reduced after 4 weeks of discontinuation.