Stomach acid is the hydrochloric acid in gastric juice, which is continuously secreted by the cells lining the stomach glands. Its main function is to promote the digestion of ingested nutrients and to kill bacteria in food. If too little acid is secreted, it will affect the digestive and absorption functions of the digestive organs, risking nutritional deficiencies; however, excessive secretion of stomach acid is also harmful to the body, with the possibility of ulcer formation in severe cases, resulting in clinical manifestations such as heartburn, acid reflux and stomach pain. Acid reflux is often the first manifestation of excessive gastric acid. Due to the excessive secretion of gastric acid by cells in the stomach lining, coupled with abnormal gastric peristalsis causing upward reflux of gastric acid, there is usually reflux of gastric contents through the esophagus to the oral cavity, which is common in patients with reflux esophagitis and functional dyspepsia. In severe cases, stomach acid can even back up into the trachea, causing coughing symptoms and stimulating the sympathetic nerves, which can lead to asthma. Stomach pain is also a common symptom of hyperacidity. Due to the increased sensitivity of the gastric mucosa to stomach acid caused by excessive secretion of stomach acid, the pain is located in the upper abdomen and is mostly cyclical, alternating between episodes and remissions, with accompanying symptoms such as belching, loss of appetite and nausea. Chronic hyperacidity is associated with a risk of peptic ulcers. In conclusion, symptoms of hyperacidity are often characterized by acid reflux, heartburn and stomach pain, which will affect normal life for a long time.