An irritation, inflammation, erosion or infection of the stomach lining. It can be acute or chronic. Gastritis can be present with either a gastric erosion or gastric ulcer. An infection with the bacteria Helicobacter pylori (H. pylori) can increase the incidence and severity of the disease. The following conditions increase the risk of this disorder: drinking alcohol, use of nonsteroidal anti-inflammatory drugs / NSAIDs (ibuprofen, naproxen, aspirin), smoking, and serious illness or stress (such as an infection or trauma).