There are several possible reasons for a baby to go from having phlegm to having no phlegm. One is that the original baby’s phlegm has been relieved with the inflammation in the throat and there is no discharge or no excessive discharge from the throat. The first is to determine whether the previous respiratory infection has been actively treated, if there is active treatment, the condition is in remission, from phlegm to no phlegm which is a normal situation. The second one is to determine the swallowing action of the baby, because as the baby gets older, it may learn to swallow sputum, and the movement of the larynx should be observed. If there are swallowing movements, it may be that the baby swallows this sputum in, which is not much of a hindrance, and there are usually no obvious side effects or other major hindrances. Thirdly, it depends on whether there are other factors, such as the baby may have little sputum itself, or spit it out due to the spitting action, or it is discharged through salivation of these things, and there is no need to worry too much about the absence of sputum.