Cough is a common symptom of respiratory diseases and has a high clinical incidence, accounting for about 30% or more of the respiratory outpatient volume. Moreover, the etiology of cough is complex and extensive, especially in patients with chronic cough with no obvious abnormalities on chest imaging, such patients are most likely to be neglected by clinicians, and many patients are misdiagnosed as “bronchitis” for a long time , ineffective treatment with a large number of antibacterial drugs, or repeated various examinations due to unclear diagnosis, delaying the condition. This causes great distress to patients Classification and causes of cough (by time of onset): Acute cough: Duration greater than 3 weeks; Sub-acute cough: Duration 3 to 8 weeks; Chronic cough: Duration less than 8 weeks. 1. Acute cough ① Common cold is the most common cause of acute cough; ② Other causes include: acute bronchitis, acute sinusitis, allergic rhinitis, acute attacks of chronic bronchitis, bronchial asthma (asthma for short), pneumonia, etc. The most common causes of subacute cough are: post-infectious cough (post-cold cough), rhinitis and sinusitis, bronchial asthma, bronchitis. Pneumonia, etc. 3. Chronic cough Chronic cough has more causes and can usually be divided into two categories: (1) X-ray chest films with clear lesions: e.g. pneumonia, tuberculosis, bronchiectasis, lung cancer, pulmonary fibrosis, etc. (2) Those with no obvious abnormalities on X-ray chest radiographs: cough is the main or only symptom, and the medical profession usually refers to cough of unknown origin, without obvious lesions on chest radiographs, for more than eight weeks as chronic cough. Common causes are: ① Cough variant asthma (CVA): Cough variant asthma is a type of asthma whose onset is related to allergies, it is mainly manifested by coughing, which is more common in outpatient clinics and accounts for about 27% of chronic coughs. Patients show sensitivity to cold air or odors and start with paroxysms. The only symptom is an irritating cough or choking cough. Patients often have chest tightness but do not feel like wheezing, and their symptoms worsen at night. They mostly have a history of allergies or family history of allergen exposure, and are often accompanied by allergic rhinitis. Further development leads to wheezing. Patients with positive bronchodilation or excitation tests on pulmonary function tests are the main basis for diagnosis. If diagnosed early the condition can be controlled early. Upper airway cough syndrome (UACS): Mostly caused by various rhinitis, sinusitis, nasal polyps, etc. Patients often have a backward flow of nasal mucus, which can also be caused by chronic pharyngitis. Patients often have symptoms of runny nose, sneezing, nasal congestion, and pharyngeal discomfort, mostly due to chronic cough caused by local irritation. Eosinophilic bronchitis (EB): It is a kind of bronchitis characterized by infiltration of eosinophils in the body, often showing a chronic irritating dry cough with a little white mucous sputum, coughing during the day and night, patients are often sensitive to odors or cold air, and a large number of eosinophils can be detected in peripheral blood or sputum to confirm the diagnosis.