Gastritis usually develops when your stomach's protective layer becomes weakened or damaged. A mucus-lined barrier protects the walls of your stomach from the acids that help digest your food. Weaknesses in the barrier allow your digestive juices to damage and inflame your stomach lining.
A number of factors can contribute to or trigger gastritis, including:
• Bacterial infection. People infected with Helicobacter pylori can experience gastritis — most commonly chronic gastritis. Half the world's population is thought to be infected with this bacterium, which passes from person to person. But the majority of those infected don't experience any complications of H. pylori infection. In some people, H. pylori may break down the stomach's inner protective coating, causing changes in the stomach's lining. The reason why some people experience complications from H. pylori infection and others don't isn't clear. However, doctors believe vulnerability to the bacterium could be inherited or it could be caused by lifestyle choices, such as smoking and high stress levels.
• Regular use of pain relievers. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen (Advil, Motrin, others) and naproxen (Aleve), can cause both acute gastritis and chronic gastritis. Using these drugs regularly or taking too much of these drugs may reduce a key substance that helps preserve the protective lining of your stomach. Stomach problems are less likely to develop if you take NSAIDs only occasionally.
• Excessive alcohol use. Alcohol can irritate and erode your stomach lining, which makes your stomach more vulnerable to digestive juices. Excessive alcohol use is more likely to cause acute gastritis.
• Stress. Severe stress due to major surgery, traumatic injury, burns or severe infections can cause acute gastritis.
• Bile reflux disease. Bile — a fluid that helps you digest fats — is produced in your liver and stored in your gallbladder. When it's released from the gallbladder, bile travels to your small intestine through a series of thin tubes. Normally, a ring-like sphincter muscle (pyloric valve) prevents bile from flowing into your stomach from your small intestine. But if this valve doesn't work properly, or if it has been removed because of surgery, bile can flow into your stomach, leading to inflammation and chronic gastritis.
• Your own body attacking cells in your stomach. Called autoimmune gastritis, this rare condition occurs when your body attacks the cells that make up your stomach lining. This produces a reaction by your immune system that can wear away at your stomach's protective barrier. Autoimmune gastritis is more common in people with other autoimmune disorders, including Hashimoto's disease, Addison's disease and type 1 diabetes. Autoimmune gastritis can also be associated with vitamin B-12 deficiency.
• Other diseases and conditions. Gastritis may be associated with other medical conditions, including HIV/AIDS, Crohn's disease, parasitic infections, some connective tissue disorders, and liver or kidney failure.