[6][7] Less common causes include alcohol, smoking, cocaine, severe illness, autoimmune problems, radiation therapy and Crohn's disease.

[1] Other conditions with similar symptoms include inflammation of the pancreas, gallbladder problems, and peptic ulcer disease.

[15][1] Helicobacter pylori colonizes the stomachs of more than half of the world's population, and the infection continues to play a key role in the pathogenesis of a number of gastroduodenal diseases.

[6][7] More than 80% of individuals infected with the bacterium are asymptomatic and it has been postulated that it may play an important role in the natural stomach ecology.

The National Health Service of the United Kingdom advises avoiding spicy, acidic or fried foods which may irritate the stomach.

[19] Acute erosive gastritis typically involves discrete foci of surface necrosis due to damage to mucosal defenses.

[20] NSAIDs inhibit cyclooxygenase-1, or COX-1, an enzyme responsible for the biosynthesis of eicosanoids in the stomach, which increases the possibility of peptic ulcers forming.

It does, however, erode the mucosal lining of the stomach; low doses of alcohol stimulate hydrochloric acid secretion.

[20] The immune system makes proteins and antibodies that fight infections in the body to maintain a homeostatic condition.

[24] In some cases bile, normally used to aid digestion in the small intestine, will enter through the pyloric valve of the stomach if it has been removed during surgery or does not work properly, also leading to gastritis.

Gastritis may also be caused by other medical conditions, including HIV/AIDS, Crohn's disease, certain connective tissue disorders, and liver or kidney failure.

Intestinal metaplasia typically begins in response to chronic mucosal injury in the antrum and may extend to the body.

In incomplete metaplasia, the epithelium assumes a histologic appearance closer to that of the large intestine and frequently exhibits dysplasia.

These scores (0–3) are used in the OLGA staging assessment in each 10 compartment:[28] Antacids are a common treatment for mild to medium gastritis.

[29] When antacids do not provide enough relief, medications such as H2 blockers and proton-pump inhibitors that help reduce the amount of acid are often prescribed.

In 1854, Charles Handfield Jones and Wilson Fox described the microscopic changes of stomach inner lining in gastritis which existed in diffuse and segmental forms.

Shields Warren and Willam A. Meissner described the intestinal metaplasia of the stomach as a feature of chronic gastritis.