Constant cough without sputum may be caused by physical and chemical stimulation, allergy, infection, bronchopulmonary cancer, cardiac insufficiency and so on. 1. Stimulation of various physical and chemical factors: If the patient has a long history of smoking, due to long-term smoke stimulation, it may cause the patient to have a dry cough with no sputum. 2. Allergy: Generally speaking, food, drug, pollen or paint allergy may cause dry cough. Allergic factors can cause an increase in respiratory secretions. 3. Various infections: such as chlamydia, mycoplasma, tuberculosis bacillus, fungi, viral infections, etc., may cause irritation of the respiratory tract, and it is unlikely that the increase of mucus secretion will cause the patient to have a dry cough. 4. Bronchopulmonary cancer: bronchopulmonary cancer may also cause prolonged cough without sputum. 5. Cardiac insufficiency: patients with cardiac insufficiency often have cough at night, most of which is caused by lung infection due to pulmonary stasis, thus leading to dry cough. It is recommended to go to the regular hospital to clarify the cause of the disease and carry out targeted treatment.