It is common to see patients who present to the clinic with cough as their main or only symptom, often for more than 8 weeks, without fever and with a normal chest x-ray. These unexplained chronic coughs may be related not only to the respiratory system, but also to the ear, nose, and throat, the digestive system, and the use of medications. The common causes include the following: 1. GERD cough This type of cough is mainly due to the reflux of stomach acid and other gastric contents into the esophagus, resulting in a clinical syndrome highlighted by coughing. Therefore, the cough is usually accompanied by typical reflux symptoms, such as heartburn (burning sensation behind the sternum), acid reflux, belching, etc. The cough is usually dry or a small amount of white mucous sputum. The cough is usually dry or with a small amount of white sticky sputum. The cough is easily triggered or aggravated after eating acidic or fatty foods. 2. Upper airway cough syndrome (also known as postnasal drip syndrome) Nasal diseases may cause secretions to flow backwards to the postnasal area and throat, directly or indirectly stimulating cough receptors and leading to cough symptoms. In addition to cough and sputum, these patients may also exhibit nasal congestion, increased nasal secretions, frequent throat clearing, adherence of throat mucus, postnasal drip flu, and some patients may also have obvious nasopharyngeal symptoms such as sneezing, throat itching, sore throat, and foreign body or burning sensation in the eyes. 3.Cough variant asthma This is a special type of asthma, but there are no obvious signs or symptoms such as wheezing and shortness of breath common in ordinary asthma patients, cough is its only or main clinical manifestation, but these patients have airway hyperresponsiveness. The main manifestation is an irritating dry cough, usually more intense, with nocturnal cough as an important feature. Cold, cold air, dust and fumes can easily trigger or aggravate the cough. 4. Eosinophilic bronchitis This type of disease is a non-asthmatic bronchitis characterized by airway eosinophil infiltration, negative airway reactivity, mainly manifesting as chronic cough that responds well to glucocorticoid therapy. The main symptom is a chronic irritant cough, often the only clinical symptom, with a dry cough or a little white mucous sputum, which can occur during the day or at night. Some patients are sensitive to fumes, dust, odors or cold air, which are often triggers for coughing. Patients in this category usually do not have symptoms such as shortness of breath and dyspnea. 5. Taking angiotensin-converting enzyme inhibitor (ACEI) drugs Patients with hypertension often take angiotensin-converting enzyme inhibitor (ACEI) antihypertensive drugs, and cough is the most common adverse effect of taking ACEI antihypertensive drugs, with an incidence of about 10% to 30%, accounting for 1% to 3% of the causes of chronic cough. These patients usually have cough relief after discontinuation of ACEI drugs, and the cough usually disappears or is significantly reduced after 4 weeks of discontinuation.