Helicobacter pylori (H.pylori) is a bacteria that can infect the stomach and cause irritation or inflammation. In some cases it can cause ulcers in the stomach or small intestine. One test that can be used to look for infection with H. pylori is a C-13 breath test (other tests include a stool test and an upper endoscopy). For the breath test, your child will be asked to blow into a bag (to get a baseline reading). They are then given a special drink and then after a short time will be asked to blow into a bag.