The most common cause of a cough with a little blood is a violent cough caused by a respiratory disease that may destroy capillaries and bleed. In addition to coughing with blood, it can be accompanied by symptoms such as weakness, fever, peripheral discomfort, chest pain, and loss of appetite. The details are as follows: 1. Patients with bronchiectasis may see a cough with blood, and may also have a relatively large amount of hemoptysis, which may be life-threatening, so prompt medical attention is needed, often accompanied by coughing and coughing yellow pus sputum. 2. Patients with pulmonary tuberculosis may also see a cough with a little blood, which, in addition to coughing and hemoptysis, is accompanied by symptoms such as low fever in the afternoon, hot flashes and night sweats, and wasting and weakness. 3. Patients with malignant tumors of the lung may also see a cough with a little blood. Patients can also be seen coughing up a little blood, commonly in people over 40 years of age who smoke, and will also be accompanied by symptoms such as wasting, weakness, coughing, wheezing, chest tightness, etc. In addition to these respiratory diseases mentioned above, local bleeding in the mouth, such as gingivitis or nasal bleeding, or local bleeding in the pharynx, will all show symptoms of a little blood in the sputum when coughing.