This is a medical question of type : causes 
 What causes Gastritis ? 
 Common causes of gastritis include
                
- Helicobacter pylori (H. pylori) infection  - damage to the stomach lining, which leads to reactive gastritis  - an autoimmune response
                
H. pylori infection. H. pylori is a type of bacteriaorganisms that may cause an infection. H. pylori infection
                
- causes most cases of gastritis  - typically causes nonerosive gastritis  - may cause acute or chronic gastritis
                
H. pylori infection is common, particularly in developing countries, and the infection often begins in childhood. Many people who are infected with H. pylori never have any symptoms. Adults are more likely to show symptoms when symptoms do occur.
                
Researchers are not sure how the H. pylori infection spreads, although they think contaminated food, water, or eating utensils may transmit the bacteria. Some infected people have H. pylori in their saliva, which suggests that infection can spread through direct contact with saliva or other body fluids.
                
More information about Peptic Ulcer Disease and H. pylori is provided in the NIDDK health topic, Peptic Ulcer Disease.
                
Damage to the stomach lining, which leads to reactive gastritis. Some people who have damage to the stomach lining can develop reactive gastritis.
                
Reactive gastritis
                
- may be acute or chronic  - may cause erosions  - may cause little or no inflammation
                
Reactive gastritis may also be called reactive gastropathy when it causes little or no inflammation.
                
The causes of reactive gastritis may include
                
- nonsteroidal anti-inflammatory drugs (NSAIDs), a type of over-the-counter medication. Aspirin and ibuprofen are common types of NSAIDs.  - drinking alcohol.  - using cocaine.  - exposure to radiation or having radiation treatments.  - reflux of bile from the small intestine into the stomach. Bile reflux may occur in people who have had part of their stomach removed.  - a reaction to stress caused by traumatic injuries, critical illness, severe burns, and major surgery. This type of reactive gastritis is called stress gastritis.
                
An autoimmune response. In autoimmune gastritis, the immune system attacks healthy cells in the stomach lining. The immune system normally protects people from infection by identifying and destroying bacteria, viruses, and other potentially harmful foreign substances. Autoimmune gastritis is chronic and typically nonerosive.
                
Less common causes of gastritis may include
                
- Crohn's disease, which causes inflammation and irritation of any part of the gastrointestinal (GI) tract.  - sarcoidosis, a disease that causes inflammation that will not go away. The chronic inflammation causes tiny clumps of abnormal tissue to form in various organs in the body. The disease typically starts in the lungs, skin, and lymph nodes.  - allergies to food, such as cow's milk and soy, especially in children.  - infections with viruses, parasites, fungi, and bacteria other than H. pylori, typically in people with weakened immune systems.