Gastritis and bitter mouth may be H. pylori infection or indigestion, inattention to oral hygiene, oral-related diseases can also lead to bitter mouth. Mainly: First, H. pylori infection, H. pylori infection is one of the direct bacteria that induce bad breath, mostly stubborn bad breath, bad breath is difficult to remove. Second, indigestion, the spleen and stomach digestive function is reduced, can not eat into the diet in time to digest, absorb, food in the body a lot of stagnation, excessive fermentation will produce a lot of gas, gas on the reverse will appear abnormal smell. Third, do not pay attention to oral hygiene, food residues left in the mouth will be over-fermented to produce abnormal odor, people who like to eat spicy, irritating food are more likely to feel bitter mouth. Fourth, oral-related diseases, common oral diseases such as dental caries, periodontitis, pulpitis, etc., the bacteria in the mouth will breed in large quantities and produce sulfide, so it will emit the smell of corruption.