Enteritis is inflammation of the small intestine, which can also involve the stomach (gastritis) and large intestine (colitis) in some cases. Enteritis is most often caused by eating or drinking things that are contaminated with bacteria or viruses, which settle in the small intestine and cause inflammation and swelling. Other causes of enteritis include autoimmune conditions such as Crohns disease, certain drugs including NSAIDs and cocaine, damage from radiation therapy, celiac disease, tropical sprue, and Whipple disease. The inflammation can also be caused by poor blood flow or inflammatory conditions such as Crohns disease or ulcerative colitis.

There are different types of enteritis, including infectious enteritis, radiation enteritis, medication-induced enteritis, alcohol or drug-induced enteritis, enteritis related to poor blood flow, and enteritis related to inflammatory conditions. The most common type of enteritis is infectious enteritis, which is caused by viruses, bacteria, or parasites that are highly contagious and spread through contaminated food or water or through contact with another infected person or animal. Some common bacteria that cause enteritis include Salmonella, Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Shigella, and Campylobacter jejuni (C. jejuni) .

Symptoms of enteritis may include abdominal pain, diarrhea, nausea, vomiting, loss of appetite, bleeding or mucus-like discharge from the rectum, and fever. Tests may include stool culture, blood tests, and imaging tests. Treatment for enteritis depends on the cause and severity of the inflammation. Mild cases and most viral infections go away on their own within a few days, while bacterial infections may require medical attention if they last for an extended period. Prevention methods for enteritis include proper food preparation, hygiene, and cleanliness, such as washing hands after using the toilet and before eating or preparing food or drinks.