Coughing up yellow sputum in the morning may be caused by Staphylococcus aureus pneumonia, acute upper respiratory tract infection, asthma, bronchodilatation, chronic bronchitis, rhinitis and other causes. 1. Staphylococcus aureus pneumonia: Staphylococcus aureus pneumonia is an inflammatory disease caused by Staphylococcus aureus infection in the lungs. This disease is one of the reasons for coughing up yellow sputum in the morning. 2. Acute upper respiratory tract infection: Acute upper respiratory tract infection can lead to yellow sputum when complicated by bacterial infection. 3. asthma: asthma before an acute attack or when combined with bronchial infection, there will be coughing up yellow sputum symptoms, at the same time there are wheezing, shortness of breath, chest tightness and other symptoms. 4. Bronchial dilatation: coughing up yellow sputum itself is one of the main manifestations of bronchial dilatation, the patient will also have repeated hemoptysis. 5. Chronic bronchitis: chronic bronchitis expansion in the acute attack will cough up yellow sputum. Therefore, coughing up yellow sputum in the morning may also be caused by chronic bronchitis. 6. Rhinitis: Rhinitis with bacterial infection will cough up yellow sputum. Therefore, yellow phlegm in the morning should also be considered rhinitis. Individuals who experience yellow sputum in the morning are advised to seek professional medical help.