Coughing is a defensive reflex activity that occurs when the body removes secretions or foreign bodies from the respiratory tract or when the respiratory mucosa is irritated. A cough without sputum or with very little sputum is called a dry cough (dry cough). Dry cough is one of the common symptoms of clinical respiratory diseases with complex etiologies, such as chronic nasopharyngitis, acute upper respiratory tract infection, cough variant asthma, and upper respiratory tract cough syndrome. If the cough is a paroxysmal dry cough with a tickling throat, no fever, obvious symptoms when exposed to cold air or irritating odors, and ineffective treatment with antibiotics, aggravated at night or in the morning, and if there is no abnormality on CT or X-ray examination, it is likely to be an allergic cough, also called cough variant asthma or allergic bronchitis. If the dry cough is accompanied by symptoms of allergic rhinitis such as sneezing, runny nose and nasal congestion, then it may be allergic cough caused by allergic rhinitis, also called allergic rhinobronchitis. If the dry cough is prolonged and does not match any of the three diseases mentioned above, then be alert to lung cancer. Cough is the most common early symptom of lung cancer, mainly characterized by paroxysmal irritating choking cough with the feeling of coughing up. These patients usually have no sputum or only a small amount of white foamy sputum, and pus sputum may appear secondary to infection. If there is no improvement after 2 weeks of anti-infection treatment, one should be alert to the possibility of lung cancer. If there is no improvement after 2 weeks of anti-infection treatment, patients should be alerted to the possibility of lung cancer. In addition, the patient’s voice may be hoarse at different degrees from time to time, which is common among lung cancer patients. People who have no chronic respiratory disease in the past, especially those over 40 years old, should be alerted to the possibility of lung cancer if their cough persists for more than three weeks without significant improvement after active treatment, and further examination is required, and lung CT is recommended to facilitate the detection of early lung cancer. Early detection and early treatment are crucial for lung cancer patients.