Helicobacter pylori (H. pylori) is a common type of bacteria that infects the lining of the stomach and the first part of the small intestine. Most people with H. pylori never have symptoms. But in some people, the bacteria can cause problems with digestion.

H. pylori is the most common cause of peptic ulcers, which are sores that form mainly in the stomach and upper part of the small intestine. H. pylori can also cause gastritis (inflammation and irritation of the stomach lining). Without treatment, H. pylori gastritis can last a lifetime and increase the chance of developing stomach cancer.

Researchers aren't sure how people get the bacteria. H. pylori may be spread from person to person through contact with vomit, stool (poop), or saliva (spit) from an infected person. The bacteria may also be spread through contaminated food and water.

Anyone who is exposed to H. pylori can become sick with an H. pylori infection. But H. pylori infections are most common in children. Testing for the bacteria can find out if H. pylori is causing gastritis or other conditions that cause ongoing indigestion. If so, treatment can kill the bacteria so the lining of your stomach can heal.