The causes of bubbles in the saliva of full-term children include the following: 1. Symptoms caused by children suffering from mouth ulcers. Children who are infected with viruses, bacteria, and other pathogens can develop mouth ulcers. After the mouth ulcers occur, the amount of drooling will increase, and this time the children will have the symptom of drooling with bubbles, and when the mouth ulcers get better, the natural symptoms will be alleviated. 2, due to the symptoms caused by children suffering from pneumonia. After the child suffers from pneumonia, it will cause the respiratory times to accelerate significantly, the saliva can’t swallow in the digestive tract in time, which will cause the symptoms of drooling and having bubbles.