"Morning breath," the bad breath associated with waking up in the morning, is a universal condition. The reason? The reduced production of saliva while asleep.
Saliva is an integral part of your mouth's defense against bacteria. It contains enzymes that can kill or reduce bacterial growth. At night, the body's production of saliva decreases significantly, thereby allowing bacteria to flourish. The result: morning breath.
In addition to the natural decrease in saliva production during the night, breathing through the mouth instead of the nose can exacerbate the issue. Mouth breathing will cause the mouth to become even drier, allowing bacteria to grow more readily. Causes of mouth breathing can include snoring and sleep apnea.
While morning breath is not fully preventable, good overall oral hygiene can help to minimize it. The tried and true strategies of brushing and flossing, as well as gently scraping your tongue before going to bed may help. Together, these will reduce the amount of bacteria and its growth potential while you sleep.