Why Does Breath Smell Bad in the Morning?

Stinky morning breath--it happens to everyone. Bad breath comes with the sun, even when you brushed and flossed your teeth before bed and regardless of what you ate the previous day. Foul morning breath results from natural processes while you sleep. Waking with minty-fresh breath may be unrealistic, but you can help control the factors that lead to morning breath.


Bacteria naturally present in the mouth cause morning breath, says Dentist.net. The mouth contains a variety of bacteria that begin the digestive process. During the day, saliva and normal mouth movements from talking and chewing irrigate the mouth and wash away debris. Saliva production dwindles during sleep, drying the mouth and lowering the available oxygen. Anaerobic bacteria, that is, bacteria that cannot live in the presence of oxygen, flourish in dry mouths. These bacteria digest proteins lingering in the mouth from food debris caught between teeth, saliva, mucus and other cellular materials.

Sulfur Gas

The breakdown of the proteins creates sulfur gas and, consequently, bad breath. The foul-smelling gas produced during sleep dissipates once saliva production resumes, writes F.L. Suarez and colleagues in a study published the “Journal of Dental Research.” Their study measured gases present in the breath of eight healthy adults on awakening and for several hours afterwards. Three types of sulfur gas compose morning breath, most commonly hydrogen sulfate, although the amounts of gas vary from person to person. Snoring and mouth breathing increase mouth dryness and worsen morning breath.


Once saliva increases on awakening, the researchers write, other breath-freshening techniques make little difference in dispelling morning breath. Regardless of whether the study participants brushed their teeth, used mouthwash, ate breakfast or simply drank a glass of water, sulfur gases decrease at similar rates during the first hour the participants were awake. Toothbrushing has minimal effect on morning breath, Suarez concludes, but a hydrogen peroxide rinse is more effective.


You cannot eliminate morning breath because it is a simple function of reduced saliva and a temporary proliferation of a specific type of bacteria. Morning breath can be reduced with good oral hygiene, however, suggests the OraMD website. Removing plaque through regular brushing, flossing and professional cleanings reduces the debris on which anaerobic bacteria feed. Tooth decay and gum disease caused by improper dental hygiene encourage bacteria and add to the problem, says MayoClinic.com. Alcohol and certain medications cause mouth dryness and will worsen morning breath.


Bad breath, especially in the mornings, rarely signals an underlying disease, notes Dentist.net. Consult your health-care provider if you notice a sudden increase in bad breath or if you develop a fever. The presence of phlegm contributes to morning breath and may be a sign of an infection.