Coughing up blood in sputum with cold may be caused by rupture of blood vessels in the respiratory mucosa, or it may be caused by other diseases, such as bronchial dilatation, tuberculosis and lung cancer. 1. Respiratory mucosal blood vessel rupture: if the patient has a cold and coughs violently, it may lead to the rupture of the capillaries of the respiratory mucosa, and at this time, the patient will have the symptom of blood in sputum. 2. Bronchial dilatation: bronchial dilatation is caused by recurrent or persistent respiratory tract infections, chronic inflammation, etc., which often results in chronic cough, sputum, hemoptysis, etc., and so the patient will show blood in sputum. 3. Tuberculosis: Tuberculosis is mainly caused by Mycobacterium tuberculosis infection, and patients will have hemoptysis, low fever, cough and other symptoms. Patients with tuberculosis often have the symptom of blood in sputum. 4. Others: such as lung cancer patients may also have the symptom of blood in sputum. The symptoms of blood in sputum can also be caused by other diseases. If the symptoms do not get better or worsen, it is recommended to consult a doctor in time, complete the relevant examination, clarify the cause of the disease, and actively cooperate with the doctor for treatment so as to avoid delaying the condition.