The main reasons for acidity in the mouth after meals are: 1, dietary factors, mainly eating fermented foods, such as bread, steamed buns, sugary foods such as pastries, cookies, acidic foods such as oranges, kiwis, the food in the mouth chewing and salivary enzymes reaction will appear acid. 2, gastroesophageal reflux, after eating can stimulate the stomach wall cells to secrete a lot of gastric acid digestion food, when the lower esophageal sphincter muscle relaxation. When the stomach acid and acidic contents of the stomach can be refluxed to the esophagus and the oral cavity, the mouth acid. 3, H. pylori infection, when the stomach H. pylori infection, the oral cavity will also have a large number of H. pylori infection growth, after eating food residues in the role of H. pylori will produce acidic substances resulting in acid mouth.