There are many reasons for the odor of the mouth, the most common is caused by oral diseases and digestive system diseases, to find out the specific cause and treat the symptoms. Oral disease: the most common cause of oral odor is carious disease and periodontitis. Due to the presence of a large number of bacteria in the mouth of patients with cavities and periodontitis, this will cause the mouth to produce odor. The caries and periodontitis are produced by the bacteria in the mouth, these bacteria are harmful bacteria, after treating the caries and periodontitis, the oral odor will disappear slowly. You should keep good oral hygiene, apply mouthwash to maintain the oral flora environment, go to the hospital regularly to check the oral cavity, and deal with the problem in time once found. Digestive system diseases: gastrointestinal tract diseases, such as peptic ulcers, chronic gastritis, etc. will be accompanied by oral odor children. The Helicobacter pylori that causes these diseases is the main cause of oral odor. After treatment, oral odor will be slowly reduced. For the existence of oral odor should be timely examination, to focus on oral diseases and digestive system diseases, according to the specific test results to treat, so as to completely solve the problem of oral odor.