There are many reasons for the symptoms of bitter mouth, which may be related to some diseases of the oral cavity or systemic diseases of the whole body. 1.Oral diseases Oral diseases that most commonly cause bitterness in the mouth are caries and periodontitis. For caries and periodontitis, timely treatment is necessary. To treat caries, we should use filling treatment to remove the decayed tissue and decayed matter on the teeth, and then fill up the teeth with filling material, so that the caries can be controlled. The main treatment for periodontitis is to use the basic treatment method to remove the plaque and calculus and other irritants around the teeth. After regular and timely treatment, after treating the caries and periodontitis, the symptoms of bitter mouth will be slowly relieved. 2.Systemic diseases The systemic diseases that cause bitter mouth are mainly the digestive system diseases. For example, liver, stomach and other digestive organs will lead to bitter mouth if there is a disease. These digestive system diseases should be treated promptly in order to solve the symptoms of bitter mouth. Therefore, oral diseases and digestive system diseases are the most common causes of bitterness. It is necessary to go to the hospital to examine the specific cause of the disease in time and make the right treatment according to the cause.