When you are asleep, saliva production in your mouth decreases. Since your saliva is the mouth’s natural mouthwash, most people experience morning breath. Bacteria found on teeth in the crevices and on the taste buds of the tongue, break down the food particles, which produce sulfur compounds. It is actually these sulfur compounds which give our breath a bad odor. During desk, your saliva helps to wash away bacteria and food particles. Your saliva also helps to dissolve the foul smelling sulfur compounds.
Chronic, long-term mouth odor can be a sign of more serious illness. See your dentist if this is a concern.