Most of the causes of bad breath are due to oral diseases or digestive disorders, etc., and should be treated accordingly. After actively treating oral diseases or digestive diseases, bad breath will disappear naturally. 1. Poor oral hygiene: a large number of plaque stones can cause bad breath, in addition to oral diseases, such as periodontitis, caries, periapical periodontitis, etc. These oral diseases can also cause bad breath, need to go to the dentist for further examination and treatment. 2. Diseases of the digestive system: can cause bad breath, such as gastritis, gastric ulcer, gastric cancer patients can only manifested as bad breath, without any epigastric pain symptoms. Therefore, in the case of bad breath, it is recommended to do a gastroscopy to further exclude gastric lesions. Additionally. Helicobacter pylori infection can also lead to bad breath, and after standardized and systematic eradication of Helicobacter pylori, the sense of bad taste in the mouth can be greatly reduced.