Gastritis is a condition characterized by inflammation, irritation, or erosion of the stomach lining, which is also known as the gastric mucosa. This inflammation can be short-term (acute gastritis) or develop gradually over time, leading to a long-lasting condition (chronic gastritis). The severity of gastritis varies; in mild cases, it may cause little to no symptoms, while in more severe cases, it can lead to ulcers, internal bleeding, and an increased risk of stomach cancer.

The stomach lining produces mucus to protect itself from digestive acids, but when this protective barrier is weakened due to various factors, stomach acids can irritate or damage the tissues, leading to inflammation. Gastritis can be caused by infections, prolonged use of certain medications, excessive alcohol consumption, chronic stress, or autoimmune conditions.