Colds are acute upper respiratory tract infections. For a 40-day-old baby with a cold, babies with mild symptoms and good resistance may recover on their own, while some other babies are more serious and usually cannot recover on their own. If a 40-day-old baby has a mild cold, the baby’s own resistance is relatively strong, and may be able to recover within a week or so. If the 40-day-old baby cold triggered a fever, and fever of 38 ℃ or more, accompanied by coughing, choking and other symptoms, the condition is more serious, can not be self-healing, should go to the hospital as soon as possible to receive formal treatment, so as not to develop into pneumonia. 40 days of the baby’s physical development is not perfect, resistance is not strong, once a cold occurs, not timely treatment, may lead to more serious conditions. Therefore, if a 40-day-old baby has a cold, it is recommended to go to the pediatrics department of a regular hospital as soon as possible for standardized treatment by a professional pediatrician.