The first reaction when you have phlegm in your throat is to cough, but coughing is not a very good option. This is because every time you cough, in order to reach the coughing effect, the body has to do a breath hold, and during the breath hold there is a part of the airway that needs to be constricted and spasmed, and the spasmodic force is used to expel the phlegm out. But this process does not really expel phlegm from the bottom, but pinches out from the halfway point, and some of the phlegm is pushed up into the lungs by the inward force. Therefore, if you have phlegm, it is recommended to cough gently and silently. Since a silent cough is applied from the bottom of the diaphragm, there is no phlegm going down into the lungs, and basically all the phlegm is expelled by the airflow, leaving no residual problems.