There are many reasons for not coughing up blood in sputum, which may be related to tuberculosis, chronic pharyngitis, bronchial dilatation and other diseases. 1. Tuberculosis: mainly due to the infection of tuberculosis mycobacteria, the disease will lead to the patient’s body in a hypersensitive state, tuberculosis lesions in the active phase, thus increasing capillary permeability, easy to cause blood in sputum. 2. Chronic pharyngitis: usually developed from acute pharyngitis, in the acute phase there will be coughing, sputum with blood symptoms, the development of the late stage, usually no obvious cough, but the pharyngeal part of the inflammation and edema will cause blood in the sputum, and the inflammation stimulation, mucous membrane rupture related. 3. Bronchial dilatation: mainly due to the irreversible expansion of the bronchial tubes or fine bronchial tubes, the majority of patients will cough repeatedly, but a small number of patients do not have a significant cough, there is blood in the sputum, a large number of hemoptysis and other symptoms, if repeated coughing, stimulation of the capillaries after the symptom will be significantly aggravated. Not coughing up blood in sputum, in addition to the above factors, may also be associated with pulmonary fibrosis, lung cancer, nasal blood secretion backflow to the throat to cough up, gastrointestinal bleeding mistakenly inhaled into the airway with sputum coughed up, etc., should be done as soon as possible sputum bacterial culture, lung CT, tumor markers screening and other tests to identify the cause of the disease, standardized treatment under the direction of the doctor.