Cough is a common clinical symptom. Clinically, cough is usually referred to as chronic cough of unknown origin, or chronic cough for short, when cough is the only symptom or the main symptom for more than 8 weeks and there are no obvious abnormalities on chest X-ray. There are two main categories of cough etiology: infectious and non-infectious. Most chronic coughs have non-infectious factors. Due to the lack of typical symptoms associated with chronic cough and the absence of abnormalities on chest X-ray, many patients are prone to long-term misdiagnosis and mismanagement of non-infectious cough, most commonly as “bronchitis or chronic bronchitis”, which often leads to unnecessary trial of antibiotic therapy, with the direct consequence of antibiotic abuse and a rapid increase in bacterial resistance. The direct consequence is the rapid increase of antibiotic abuse and bacterial resistance. In some patients, the diagnosis is not clear for a long time, and various tests such as chest X-ray, CT and even fibrinoscopy are repeatedly performed, which not only causes a great waste of medical resources and increases the economic burden of patients, but also brings great distress to patients’ lives and even to their hearts. I. Classification of coughs Usually divided into 3 categories according to time: acute cough for 3 weeks. Subacute cough 3 – 8 weeks. Chronic cough ≥ 8 weeks. II. Common causes of acute and subacute coughs : Common causes of acute coughs are the common cold, followed by acute bronchitis, allergic rhinitis, acute rhinitis, etc. The common causes of subacute cough are post-cold cough (also called post-infection cough), other causes such as subacute sinusitis, bronchial asthma, etc. There are more causes, usually one type of cough with obvious lesions on initial X-ray chest images such as pneumonia, tuberculosis, lung cancer, etc. The other type of cough with no obvious abnormalities on chest images and cough as the main or only symptom is usually referred to as chronic cough of unknown origin (referred to as chronic cough). ). Three p common causes of chronic cough: Smoking is probably one of the most common causes of cough in smokers, but smokers usually do not actively seek medical attention for chronic cough. The causes of chronic cough in nonsmokers are more complex and are not only related to the respiratory system, but also to the nasopharynx and digestive system. Various causes, such as postnasal drip syndrome (PNDS) due to nasal diseases like non-allergic rhinitis, allergic rhinitis, vasodilatory rhinitis and chronic bacterial sinusitis, as well as cough variant asthma (CVA), gastroesophageal reflux cough (GERD), chronic bronchitis, eosinophilic bronchitis (EB), taking angiotensin-converting enzyme inhibitor (ACEI) antihypertensive drugs are all common causes of chronic cough. Others include bronchiectasis, endobronchial tuberculosis, allergic cough, post-cold cough, interstitial pneumonia, idiopathic cough, and psychogenic (psychogenic cough) cough.