H. pylori infection occurs when a bacterium called Helicobacter pylori (H. pylori) infects your stomach or the first part of your small intestine.

What is it?

  • H. pylori infection occurs when a bacterium called Helicobacter pylori (H. pylori) infects your stomach or the first part of your small intestine.
  • H. pylori infection is thought to be present in about half the people in the world. For many people, H. pylori infection causes no signs or symptoms and doesn't lead to any complications. But for others, H. pylori can lead to serious complications, such as ulcers and stomach cancer.


Most cases of H. pylori infection produce no signs or symptoms. Signs or symptoms that can occur with H. pylori infection include:

  • An ache or burning pain in your abdomen
  • Nausea
  • Vomiting
  • Frequent burping
  • Bloating
  • Weight loss


H. pylori infection is caused by the H. pylori bacterium. H. pylori is primarily passed from person to person through direct contact with saliva or fecal matter. H. pylori can also be spread through untreated water.

H. pylori bacteria enter your body through your mouth and passes into your digestive system. The stomach and its stomach acid make a hostile environment for many bacteria. But the H. pylori bacterium is especially well-adapted for survival in the stomach. It produces an enzyme that, through a series of biochemical processes, creates a low-acid buffer zone for itself.

Risk factors

Many people contract H. pylori as children. Contracting H. pylori in adulthood is much less common. Risk factors for H. pylori infection are related to living conditions in your childhood, such as:

  • Living in crowded conditions. You have a greater risk of H. pylori infection if you live in a home with many other people.
  • Living without a reliable supply of hot water. Having a reliable hot water supply can help you keep your living area clean and reduce your risk of H. pylori.
  • Living in a developing country. People living in developing countries, where crowded and unsanitary living conditions may be more common, have a higher risk of H. pylori infection.
  • Living with someone who has an H. pylori infection. If someone you live with has H. pylori, you're more likely to also have H. pylori.


Many people with H. pylori infection will never have any signs or symptoms and will never develop complications. Others will develop serious complications. It's not clear why this is.

Complications associated with H. pylori infection include:

  • Open sores (ulcers) in your stomach and small intestine. H. pylori infection causes the majority of these ulcers.
  • Inflammation of the stomach lining. H. pylori infection can irritate the lining of the stomach, causing inflammation (gastritis).
  • Stomach cancer. H. pylori infection is a strong risk factor for certain types of stomach cancer, including adenocarcinoma and gastric mucosa-associated lymphoid tissue (MALT) lymphoma.


Tests and procedures used to determine whether you have an H. pylori infection include:

  • Blood test. Analysis of a blood sample may reveal signs of an H. pylori infection in your body. A blood sample is usually collected by pricking your finger.
  • Breath test. During a breath test, you drink a solution that contains radioactive carbon molecules. If you have an H. pylori infection, the radioactive carbon is released when the solution is broken down in your stomach. Your body absorbs the radioactive carbon and expels it when you exhale. You exhale into a bag and your doctor uses a special device to detect the radioactive carbon.
  • Stool test. A laboratory test called a stool antigen test looks for foreign proteins (antigens) associated with H. pylori infection in your stool.
  • Using a flexible scope to see inside your stomach. During an endoscopy exam, your doctor threads a long flexible tube equipped with a tiny camera (endoscope) down your throat and esophagus and into your stomach and duodenum. Using this instrument, your doctor can view any irregularities in your upper digestive tract and remove tissue samples (biopsy). These samples are analyzed for H. pylori infection.