I. Classification of cough according to time Acute cough <3 weeks; subacute cough 3 - 8 weeks; chronic cough R8 weeks II Definition of chronic cough Chronic cough involves a variety of etiologies, part of which has bronchopulmonary pathology, such as bronchodilation, bronchial tuberculosis, etc.; the other part does not have bronchopulmonary pathology, and what we currently refer to as "chronic cough The term "chronic cough" currently refers to patients who have no obvious lesions on X-ray chest radiographs and whose cough is the only or main clinical symptom. This includes cough variant asthma, upper airway cough syndrome, eosinophilic bronchitis, gastroesophageal reflux cough, allergic cough, and post-infectious cough, with chronic bronchitis accounting for a small percentage. In a small number of patients, chronic cough is associated with medications (e.g., "Prilosec" antihypertensive drugs) or with small joint instability in the cervical and thoracic spine. Some chronic coughs may involve an overlap of multiple etiologies (e.g., cough variant asthma combined with gastroesophageal reflux). Second, eosinophilic bronchitis (EB) accounts for about 10%-20% of chronic coughs and often presents as an irritating dry cough that can occur both during the day and at night, with occasional small amounts of mucus sputum, mostly due to inhalation of irritants, usually more common in smokers. Some patients are sensitive to fumes, dust, odors or cold air, which are often triggers for coughing. Its diagnosis relies mainly on induced sputum examination (induced sputum eosinophil ratio >2.5%, and normal X-ray chest, CT, pulmonary ventilation function, and negative bronchial excitation or bronchodilatation test). Treatment such as glucocorticoid inhalation is effective. C. Upper airway cough syndrome (UACS) UACS is a common nasal disease that causes coughing mainly during the daytime and less often after sleep. Nasal congestion, runny nose, sneezing and other symptoms. It is often triggered or aggravated by a cold. Sometimes there is hoarseness, and even speech can trigger a cough. In addition to nasal diseases, UACS is often associated with diseases of the throat and tonsils, such as allergic pharynx or non-allergic pharyngitis, chronic tonsillitis, and laryngitis. Treatment is mainly directed at nasopharyngeal disorders. Fourth, gastroesophageal reflux-related cough (GERC ) GERC accounts for about 10% of chronic cough, which can be caused by acid reflux or but only reflux. In addition to cough, it is often accompanied by acid reflux, belching, heartburn, early satiety, postprandial fullness, epigastric distention and pain, etc. Some patients have only pharyngeal discomfort, retrosternal discomfort, or have symptoms such as dry mouth and bitterness. 24-hour gastric acid monitoring is feasible, and the diagnosis is clarified by understanding the size of the correlation between cough and gastric acid The size of the correlation between cough and gastric acid reflux is clearly diagnosed, and the main treatment is to inhibit gastric acid and strengthen gastric motility; if necessary, a visit to the gastroenterology department is required to clarify the cause of reflux. V. Common auxiliary examinations for chronic cough 1. Chest X-ray examination: if the cough is >2 weeks old, routine chest X-ray examination is required to exclude chronic cough due to bronchial and pulmonary pathology; only if no obvious abnormality is seen does the cough fall into the category of “chronic cough” as defined above, and CT examination of the chest is feasible if necessary. 2. Pulmonary function tests: A positive bronchial excitation test or diastolic test is an important diagnostic criterion for cough variant cough. 3. Induced sputum cytology analysis: a sputum eosinophil ratio greater than 2.5% is the most important diagnostic criterion for the diagnosis of eosinophilic bronchitis. Patients with cough variant asthma may also present with an elevated sputum eosinophil ratio, while the efficacy and course of treatment can be evaluated by dynamic observation of the induced sputum eosinophil ratio. 4. 24-hour gastric pH testing is the main diagnostic tool for the diagnosis of GERD cough. In addition to this, targeted sinus CT, allergen skin test, serum IgE, and fiberoptic bronchoscopy can be performed if necessary to clarify the etiology.