A foul odor often wells up in the throat in several ways: First, there is a chronic stomach or esophageal lesion. The patient has a history of chronic gastritis, there is a hangover in the stomach, this hangover in the morning or other nausea, feel a sour odor welling up. Second, the presence of a chronic infection foci in the throat, the teeth can also appear chronic infection foci, such as chronic tonsils with purulent secretions attached to the surface, or even purulent white particles, when the mouth has a foul odor. Third, there are dental caries, the mouth will also feel a foul odor. The patient himself may not be able to feel obviously, and the people in the neighborhood are obviously able to feel it.