Cough is the most common symptom of respiratory diseases. By nature, cough can be divided into dry cough and wet cough. A dry cough is a cough without sputum or with a small amount of white mucus sputum. There are many causes of dry cough, but in general they are divided into two areas: First: non-infectious diseases. Second: Infectious diseases at their first onset (also known as the early stages of the disease). Non-infectious diseases include the following: eosinophilic bronchitis, cough variant asthma, allergic cough, gastroesophageal reflux cough, primary pulmonary hypertension, laryngeal cancer, mitral stenosis, tracheobronchial bifurcation irritation by pressure, tracheal or bronchial tumor, tracheal or bronchial foreign body, pleurisy, pneumothorax, external ear canal irritation or cardiogenic cough. Dry cough and throat itch can also occur at the beginning of infectious diseases, commonly in the following cases: acute pharyngitis, chronic pharyngitis, early acute tracheobronchitis, laryngeal and pulmonary tuberculosis. The above description shows that the causes of dry cough are not limited to the respiratory system, but the simplest circulatory system diseases may also present this symptom.