When a four-month-old baby has a cold, fever, and cough, it is recommended to follow the doctor’s instructions for medication treatment, maintain a relaxed attitude, and ensure the baby drinks plenty of warm water. Regularly check the baby’s temperature and consider physical cooling methods. Additionally, consider using expectorant and cough suppressant medications or nebulizer inhalation treatment. Adjust clothing as needed with weather changes to prevent catching a cold. If symptoms are severe, seek immediate hospitalization in the pediatric department to avoid delaying the condition.