Unpleasant mouth odor, sometimes called halitosis. Bad breath is usually caused by certain foods or beverages, tobacco use, poor oral hygiene, tooth decay, a DRY mouth, periodontal disease (disease of the gums), an infection, or a medical disorder. When strong-flavored food — garlic and onions, for example — is eaten or when coffee or alcohol is consumed, they are absorbed into the bloodstream and transferred to the lungs where their odors are expelled during breathing. These odors persist in the breath until the food is eliminated from the body. When small particles of food collect between the teeth, on dentures, and on the tongue and other tissues of the mouth, they decompose and collect bacteria, which produce an offensive odor. The bacteria can also cause tooth decay, which contributes to bad breath. Removing these particles by regular flossing and brushing the teeth helps to prevent tooth decay and bad breath. Brushing the tongue and cleaning dentures will also help to prevent bad breath.