Mouth eating tastes bad, the main consideration is related to poor oral hygiene, oral diseases, neighboring organs lesions, digestive system diseases and other factors. 1. Poor oral hygiene: usually do not pay attention to personal oral hygiene, resulting in the retention of some food residues in the teeth, in the mixing and fermentation, which can produce a distinctive odor, which in turn leads to the feeling of food tasteless when eating. 2. Oral diseases: such as oral ulcers, gingivitis and other diseases, may lead to some inflammatory secretions in the affected area, in the mixture of food for chewing, there can be food odor phenomenon. 3. Diseases of neighboring organs: such as tonsillitis, purulent pharyngitis, sinusitis and other diseases, can also lead to some inflammatory secretions in the oral cavity, and then in the eating of food odor symptoms. 4. Digestive system diseases: such as reflux esophagitis, bile reflux gastritis and other diseases, can trigger the reflux of gastric contents, and acid reflux, nausea and other symptoms. In particular, acid reflux into the mouth, in the same way when eating food can appear to change the taste of the symptoms. If this phenomenon exists for a long time, attention should be paid to it, and medical examination should be conducted as soon as possible and treatment should be carried out under the guidance of the doctor.