Acid reflux in the mouth is related to non-disease factors such as diet, or it may be caused by diseases such as gastroesophageal reflux disease (GERD) due to abnormal esophageal dynamics. 1. Non-disease factors: Eating too stimulating, sweet and sour food can lead to an increase in physiological gastric acid secretion, causing acid reflux. Mental stress and excessive fatigue can lead to cerebral cortical dysfunction, causing excessive secretion of gastric acid. Irregular life, bad snacking habits, etc., can also cause acid reflux. 2.Diseases: (1) Abnormal esophageal dynamics: gastroesophageal reflux, pancreatic achalasia, secondary esophageal stenosis, etc. can lead to abnormal esophageal dynamics, resulting in acid reflux. (2) Gastric emptying obstruction: gastroparesis syndrome, pyloric obstruction, etc. can cause gastric emptying obstruction, leading to acid reflux. (3) Others: Upper gastrointestinal tract tumors such as esophageal cancer and stomach cancer can also cause acid reflux symptoms. There are many causes of acid reflux, so it is recommended to go to the hospital in time to find out the causes and get timely treatment.