When there is indigestion, the stomach takes longer to digest the food, so the food ferments badly in the stomach and produces a sour smell. The gas is also produced, causing the stomach to dilate excessively, and the burping is accompanied by the sour smell of digested food. In some people, a strong stomach fire not only causes hunger, but also constipation, and when a person has a strong stomach fire, he or she will burp up a rotten egg smell. H. pylori is an anaerobic bacterium that can survive in the acidic environment of the stomach. H. pylori not only invades the gastric mucosa, causing gastritis and gastric ulcer, but also affects the peristaltic function of the stomach, leading to indigestion and bloating. Patients with H. pylori infection in the stomach have a bad odor when they burp.