Dry cough without sputum followed by sputum may be caused by viral pneumonia, lung abscess and lung cancer combined with obstructive pneumonia. 1. Viral pneumonia: patients with viral pneumonia often show obvious symptoms of dry cough without sputum, but such patients are very easy to be combined with bacterial infections in the lungs, etc. When the disease develops into bacterial pneumonia, they may cough up sputum. 2. Lung abscess: patients with lung abscess at the early stage, especially those with hematogenous lung abscess, will show dry cough without sputum because it is difficult to cough out the abscess at the early stage, but with the development of abscess, a large amount of pus can be discharged through the bronchial tubes after the abscess breaks through the bronchial tubes, which will show sputum symptom. 3. Lung cancer combined with obstructive pneumonia: Generally, lung cancer patients at the early stage will stimulate the bronchial wall, which will cause coughing, but usually no sputum, when the tumor size gradually increases, it may cause obstructive pneumonia, which will lead to sputum coughing phenomenon. Therefore, it is suggested that patients should go to the hospital for detailed examination in time, so as to clarify the cause of the disease and target treatment.