Acid reflux in the mouth of the stomach is mainly caused by gastroesophageal reflux disease, chronic gastritis, peptic ulcer, stomach tumors and other diseases, it is recommended to consult a doctor in time to identify the cause of the disease and actively cooperate with the treatment. 1. Gastroesophageal Reflux Disease (GERD): It is a disease caused by the reflux of gastric and duodenal contents into the esophagus. Typical esophageal symptoms include reflux and heartburn, while atypical symptoms include chest pain, difficulty in swallowing, foreign body sensation at the back of the sternum, as well as acid reflux in the stomach. Extra-esophageal symptoms include laryngitis, chronic cough, asthma and so on. It is recommended to go to the hospital. 2. Chronic gastritis: mainly refers to a variety of causes of chronic inflammatory lesions of the gastric mucosa, which will increase the secretion of gastric acid, and at the same time, gastric peristalsis decreases, resulting in acid reflux in the mouth of the stomach. In addition, may also be accompanied by epigastric pain, loss of appetite, nausea and other symptoms, it is recommended to seek medical treatment. 3. Peptic ulcers: These are ulcers caused by the mucous membrane of the gastrointestinal tract being digested by pepsin or gastric acid itself, which will stimulate an increase in the secretion of gastric acid, thus leading to acid reflux in the mouth of the stomach. It may also be accompanied by bleeding, nausea, anorexia and other symptoms, and prompt medical attention is recommended. 4. Stomach tumor: stomach tumor cells invade the gastric mucosa, which will lead to decreased peristaltic function of the stomach, and there will be excessive secretion of gastric acid, which will lead to acid reflux in the stomach. It may also be accompanied by a series of manifestations such as heartburn, abdominal pain, etc. It is recommended to consult a doctor in time to clarify the cause of the disease and actively treat it. Therefore, if the patient has symptoms of acid reflux, it is recommended to consult a doctor in time to identify the cause of the disease and cooperate with the treatment.