Bitterness in the mouth when eating may be related to digestive system diseases, oral diseases, dietary factors and other reasons. 1. Digestive system diseases: such as reflux esophagitis, due to poor gastric dynamics, can lead to reflux of gastric contents, which can cause bitterness in the mouth when eating. 2. Oral diseases: such as dental caries, due to a large number of bacterial reproduction after the decomposition of food residues, can cause eating mouth bitter. 3. Dietary factors: after consuming bitter food such as bitter melon, if you continue to consume other foods, you may experience a bitter eating mouth. It is recommended that people who suffer from bitterness in the mouth need to go to the hospital in time if they have other uncomfortable symptoms, so as to clarify the cause of the disease and carry out standardized treatment under the guidance of the doctor.