Spitting yellow sputum may be caused by the following: 1. Spitting yellow sputum may be caused by bacterial infections in the bronchial lung, such as purulent bronchitis and bronchopneumonia. 2. Acute infection with tuberculosis, resulting in spitting yellow sputum. 3. Chronic respiratory diseases, such as chronic bronchitis emphysema and bronchiectasis, may also cause spitting yellow sputum in the presence of bacterial infections. 4. 4. In Chinese medicine, yellow sputum is considered to be caused by wind-heat cold or lung heat, and patients who have yellow sputum should go to the hospital for sputum culture and chest X-ray and CT lung examination to clarify the cause and then proceed with treatment.