Cough chest x-ray is normal, there may be something else going on. Common causes are acute upper respiratory tract infections, gastroesophageal reflux disease, cough variant asthma and so on. 1. Acute upper respiratory tract infection: such as tonsillitis, pharyngolaryngitis, etc., will induce a dry cough, but mostly accompanied by nasal congestion, runny nose and other upper respiratory tract symptoms of khat, some may appear low-grade fever, due to the site of the lesion in the upper respiratory tract, there will be a chest X-ray without abnormal findings. 2. Gastroesophageal reflux disease (GERD): is caused by a variety of factors in the digestive tract dysfunction, patients mainly manifested as acid reflux, heartburn symptoms, can be accompanied by chest burning sensation, hiccups, nausea, local reflux reflux stimulation of the airway mucosa, but also lead to chronic cough symptoms. 3. Cough variant asthma: it is asthma with cough as the main symptom or the only symptom, the cough is characterized by a dry cough, significant cough at night, tracheal diastolic test, positive bronchial excitation test can be clearly diagnosed. At the same time, it should be noted that many lung lesions can not be detected by chest X-ray, if the cough is more serious, it is recommended to improve the chest CT examination, and gradually investigate the causes of the cough, to avoid delaying the condition.