Coughing up yellow sputum with a cold is usually a combination of bacterial infections, but it can also be self-inflicted. Coughing up yellow phlegm with a cold is usually a combination of bacterial infections. Colds are caused by viral infections, but can also be combined with bacterial infections. Bacteria can affect the mucous membranes of the trachea and bronchial tubes, causing damage and more sputum production. Also affected by the bacterial infection, the sputum turns yellow. However, we cannot rule out the possibility that our own causes, including long-term smoking, chronic bronchitis, environmental stimuli, etc., can also cause yellow sputum coughing manifestations, only that the symptoms occur in the course of a cold, mistaken for cold symptoms. Therefore, it is recommended to consult a doctor in time, under the guidance of the doctor to carry out lung X-ray, blood tests, etc., and at the same time, according to the doctor’s instructions for treatment.