Gastric ulcers can lead to bad breath, which is mostly considered to be caused by factors such as Helicobacter pylori infection and digestive abnormalities. 1. Helicobacter pylori infection accounts for most of the causative factors of gastric ulcers. Helicobacter pylori secretes urease, protease and other substances that not only damage the gastric mucosa, but also break down the amines produced by the urea inside the stomach, which produces an irritating odor that passes through the esophagus into the oral cavity, forming bad breath. 2. Gastric ulcers also lead to digestive abnormalities, decreased peristalsis and delayed gastric emptying. Food accumulates in the stomach, and the odor produced after fermentation can also enter the mouth through the esophagus and cause bad breath. However, it should be noted that there are many other factors that can cause bad breath, such as poor oral hygiene and oral diseases. Therefore, gastric ulcers can cause bad breath, and it is recommended that patients consult a doctor in a timely manner to clarify the cause of the disease and follow the doctor’s instructions for standardized treatment.