If you have a persistent cough, you need to look for the cause and treat it for the cause to be effective. Possible causes mainly include tuberculosis, lung cancer, cough variant asthma, upper airway cough syndrome, eosinophilic bronchitis, and gastroesophageal reflux cough. Tuberculosis and lung cancer are relatively easy to understand, being tuberculosis infection of the lung and malignant tumor of the lung, respectively. Cough variant asthma is a specific type of asthma in which cough is the only or main clinical manifestation. The cough is usually a relatively intense irritating dry cough, with a pronounced cough at night. Upper airway cough syndrome, a cough syndrome due to various diseases of the upper respiratory tract, has no specificity of symptoms. Eosinophilic bronchitis is a non-asthmatic bronchitis due to eosinophil infiltration, and the cough can occur during the day and at night. Gastroesophageal reflux cough is due to reflux of gastric acid and other gastric contents into the esophagus, resulting in a cough as the prominent clinical manifestation. Most coughs occur in the daytime or in the upright position, and are aggravated by overeating, eating before bedtime, ingesting coffee, acidic or greasy foods, etc. A cough that has been bad, especially a chronic cough of more than 8 weeks, has many etiologies and requires a hospital visit to clarify the cause in order to prescribe the right medication.