Introduction Gastritis is an inflammation of the stomach lining. Many things can cause gastritis. Most often the cause is infection with the bacteria Helicobacter pylori, which also causes stomach ulcers. An autoimmune disorder, a backup of bile into the stomach, or long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, can also cause gastritis. In some cases, the stomach lining may be "eaten away," leading to sores (peptic ulcers) in the stomach or ...