Baby phlegm in the mouth may be because the baby’s laryngeal cartilage is not fully developed, can not cough up phlegm independently, this cause of phlegm will also be accompanied by respiratory changes, parents can be observed, generally do not need special treatment. The baby has phlegm may also be caused by cold, cold is a common manifestation of cough, phlegm, you can see whether the baby has a cough phenomenon. If it is caused by a cold, it needs to be treated with medication in a timely manner. If the disease is pneumonia or bronchitis, it can also lead to phlegm. If the cough is more obvious, you need to go to the hospital in time, the doctor may give the baby a blood test, chest X-ray and other tests to clarify the diagnosis. If your baby has phlegm that cannot be discharged, you can do nebulization treatment, or you can give your baby more water to help dilute the phlegm.