Drooling is expected in babies, who do not yet have full control over their mouths or swallowing muscles. But drooling is often embarrassing for children and adults. Many people may avoid discussing this symptom. Drooling can occur for many reasons. Most people drool every once in a while. It is especially common while sleeping, when a person swallows less frequently. This can cause saliva to accumulate and seep from the sides of the mouth. For those wondering how to stop drooling, the best method may depend on the cause.