Colds with yellow sputum can be caused by a combination of bacterial infections that aggravate colds, or by diseases such as bronchitis, pneumonia, or bronchiectasis. Colds are caused by viral infections and can present upper respiratory symptoms such as fever, cough, phlegm, sore throat, etc., which can worsen the condition if not intervened in a timely manner and treated appropriately. Combined with bacterial infection, it may even spread to the bronchial tubes and lungs, causing bronchitis, pneumonia, bronchodilatation and other diseases, which may lead to increased respiratory secretions and coughing up yellowish phlegm and other symptoms. After coughing up yellow sputum, you should go to the hospital as soon as possible for blood tests, C-reactive protein and other laboratory tests, and if necessary, complete chest X-ray or chest CT and other tests, to determine the cause of the disease, and then under the guidance of the physician to carry out comprehensive and standardized treatment.