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If you've been diagnosed with H. pylori, it means that you have these bacteria (germs) in your stomach. You may have symptoms of indigestion, such as stomach cramps or bloating, or you may have been told that you have an ulcer.

Doctors discovered Helicobacter pylori (H. pylori for short) nearly 25 years ago. Before then, if you had an ulcer in your stomach, you might have been given treatment to help with your symptoms. But this treatment wouldn't have gotten rid of the ulcer that was causing your pain. Nowadays, you can get rid of your symptoms for good by taking treatment that kills H. pylori.

• H. pylori infection is common.
• Most people get infected with H. pylori in childhood. But because of better living standards these days fewer children get infected now.
• If you have H. pylori infection, you're more likely to get indigestion or an ulcer.
• But most people who have H. pylori don't get any symptoms.
• Besides H. pylori, some other things can cause indigestion too. These include eating too much food, eating spicy food, stress, hiatus hernia, taking aspirin and drinking alcohol.
• If your indigestion is caused by an ulcer, getting rid of H. pylori usually leads to a cure.

To understand why H. pylori can cause problems, it helps to know something about your digestive system (the parts of your body that help break down food).

When you eat, food passes from your mouth to your stomach down a tube called the esophagus.

Your stomach holds and breaks down the food you've eaten by producing chemicals. Your stomach has two parts.^{1 2}

• The top part produces the acid that your stomach needs to break down food.
• The lower part produces other chemicals, called enzymes, which also help break down food.

When you see, smell or taste food, your brain sends signals to your stomach. Your stomach then starts making acid, ready for the arrival of your first mouthfuls of food. When the food arrives, your stomach makes more acid.

Your body has a system to stop the acid from burning your stomach. The cells on the inside surface of your stomach produce a sticky fluid called mucus. This fluid coats your stomach and stops the acid from damaging it. But if your stomach makes too much acid, it can be harmful for you.¹

Food passes from your stomach into your small intestine (gut). The part of your small intestine closest to your stomach is called the duodenum. You're most likely to get an ulcer in your stomach or your duodenum because acid can collect there.¹

Your small intestine leads into your large intestine (which is also called the colon), which then leads into your rectum. Waste products from your body are stored in your rectum before being passed out through your anus.

H. pylori is one of the many bacteria (germs) that can live in your body. It looks like a spiral tube with thin hairs at one end. If you're infected with it, H. pylori can be found in your stomach, your saliva and your stools. But you can only see it using a microscope.

H. pylori infection is hard to catch. Most people get it in childhood. For example, you may have put your finger in your mouth after touching some vomit or stools that were infected with the bacteria. Today, better hygiene in the home means that far fewer children catch the infection. And if you use basic hygiene, you needn't worry that you'll pass the bacteria on to anybody else.

When H. pylori gets into your mouth, it travels down into your stomach. Usually, most of the different kinds of bacteria that reach your stomach are killed by the acid and other chemicals that your stomach makes. But H. pylori survives by using the mucus in your stomach to protect itself. H. pylori lives in the lining of your stomach. This makes it hard for your body's immune cells to find these bacteria and kill them.³

H. pylori can harm your stomach and your duodenum (the part of your gut just under your stomach) in several ways.

• H. pylori can damage the lining of your stomach. This means that the cells underneath the lining get damaged by the acid and other chemicals in your stomach.⁴ Or the lining of your stomach can become irritated or swollen.
• It can disrupt the cells that make acid in your stomach. So these cells produce too much or too little acid. If they make too much acid your duodenum can get damaged.²
• H. pylori can cause changes in other cells in your stomach. This may lead to stomach cancer.²

Doctors and scientists are still learning about H. pylori infection, and how it's linked to problems with digestion. We know for sure that some problems are caused by H. pylori. But we're not quite sure whether some other problems are linked with H. pylori.

We've listed what we know about the problems different problems under the headings:

• Problems caused by H. pylori
• Problems that may be caused by H. pylori
• Problems not caused by H. pylori.

You'll find a brief description of each problem here.

• Stomach ulcer: This is a sore or hole in the lining of your stomach that causes a burning pain. It's also called gastric ulcer.
• Duodenal ulcer: This is a sore or hole in the lining of your duodenum, the part of your gut just under your stomach. This might cause pain in your stomach or gut, plus bloating.

About 15 in 100 people with H. pylori will get either a stomach or duodenal ulcer in their lifetime.⁵

• Gastritis: This is swelling or irritation (inflammation) of the lining of your stomach. It may or may not give you any symptoms.
• Stomach cancer: This happens when the cells in your stomach grow out of control, harming other cells around them. This problem is rare, but it's more common in people who have H. pylori.

• Non-ulcer dyspepsia: This means you have the same symptoms as someone who has an ulcer, but you don't have an ulcer. This condition is also called functional dyspepsia.

• Gastroesophageal reflux disease: This means that acid from your stomach flows back into your esophagus (the tube that leads from your mouth to your stomach), causing a burning feeling. Doctors call it GERD for short.
• Hiatal hernia: This happens when part of your stomach gets pushed up into your chest area, through a gap in your diaphragm (a large, thin muscle that separates your chest from your abdomen). A hiatal hernia can cause a burning feeling in your chest. It's sometimes called a hiatus hernia.
• Esophagitis: This is irritation or swelling (inflammation) of the lining of your esophagus (the tube that leads from your mouth to your stomach). It usually happens as a result of GERD or hiatal hernia. You may or may not have pain.

If you have certain symptoms, your doctor will advise you to have a test for H. pylori. To read more, see What are the symptoms of H. pylori?

If you have a stomach ulcer, or a duodenal ulcer or early stomach cancer, your doctor will usually advise you to have a test for H. pylori.¹ You may also have a test for H. pylori if you've had an ulcer in the past. If you have severe indigestion (burning or gnawing pain between your breastbone and belly button), you may have a test for H. pylori to see if it's causing your symptoms.

If you have H. pylori, you're slightly more likely to get stomach cancer than people who don't have these bacteria. But there are many other reasons why you might get stomach cancer. Experts don't know whether getting rid of H. pylori reduces your chances of getting stomach cancer.⁶

To read more, see How do doctors diagnose H. pylori?

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.