Gastritis occurs when the lining of the stomach becomes inflamed or swollen. Rather, gastritis is a condition that has many causes. Common to all people with gastritis is pain or discomfort in the upper part of the belly (abdomen), also called dyspepsia. The stomach lining contains special cells that produce acid and enzymes, which help break down food for digestion, and mucus, which protects the stomach lining from acid.

Gastritis may be acute or chronic. Sudden, severe inflammation of the stomach lining is called acute gastritis. Inflammation that lasts for a long time is called chronic gastritis. If chronic gastritis is not treated, it may last for years or even a lifetime.

Gastritis can be caused by irritation due to excessive alcohol use, chronic vomiting, stress, or the use of certain medications such as aspirin or other anti-inflammatory drugs.