Ulcers are open sores found in the lining of the stomach, intestines or esophagus. Stomach and intestinal ulcers are most commonly caused by Helicobacter pylori (H. pylori) bacteria. These bacteria usually live in the stomach and create ulcers when they penetrate and inflame the mucous layer in the stomach. Researchers estimate that roughly half the people in the world have an infection of H. pylori. While most people do not notice any symptoms or health complications, some people experience severe complications of the infection, including stomach cancer. Combined with antibiotic medications, omeprazole can help treat ulcers by reducing the amount of stomach acid that is produced. This prevents some of the pain associated with stomach ulcers and gives the body time to heal as the antibiotics kill the H. pylori infection.