Gastritis is an inflammation of the stomach lining that can develop suddenly (acute) or gradually over time (chronic). It may be caused by infection with Helicobacter pylori, prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs), excessive alcohol consumption, stress from severe illness, or autoimmune conditions. Symptoms often include upper abdominal pain or burning, nausea, vomiting, bloating, loss of appetite, and indigestion, though some individuals may have no noticeable symptoms. If untreated, gastritis can lead to complications such as ulcers or bleeding. Treatment focuses on addressing the underlying cause and may involve medications to reduce stomach acid, antibiotics for bacterial infection, and lifestyle modifications to protect the stomach lining.