Ulcers are erosions (wearing away or corrosion) in the lining of the stomach or duodenum. (The duodenum is the first part of the small intestines, which connects to the stomach.) An ulcer in the stomach is called a gastric ulcer. An ulcer in the duodenum is called a duodenal ulcer. Together, ulcers of the stomach and duodenum are referred to as peptic ulcers.

Most ulcers are erosions of the first layer of the inner lining. If the hole goes all the way through, this is called a perforation of the intestinal lining. This can cause shock and is a medical emergency.

Normally, the lining of the stomach and small intestines have protective mechanisms that prevent damage from the irritating acids produced in your stomach. For a variety of reasons, these protective mechanisms may become faulty, leading to a breakdown of the lining. This results in inflammation (gastritis) or an ulcer.

The most common cause of such damage is a bacterium called Helicobacter pylori. Most people with peptic ulcers have this organism living in their gastrointestinal (GI) tract. On the other hand, many people have this organism living in their GI tract but they don't get an ulcer.

Other factors make it more likely for you to get an ulcer, with or without H. pylori. Such factors include:

• Use of aspirin and nonsteroidal anti-inflammatory medications (NSAIDs) like ibuprofen or naproxen
• Excessive drinking of alcohol
• Use of tobacco, like smoking cigarettes

In addition, if you have a family history of ulcers or you are blood type 0, you are more likely to get a duodenal ulcer. There is also a rare condition called Zolliger-Ellison syndrome in which a tumor in the pancreas secretes a substance that causes ulcers throughout the stomach and duodenum.

A once popular belief was that stress causes ulcers. This is not true. Stress may make you experience more pain from an ulcer and it may make it more difficult to heal from an ulcer. But, stress does not cause an ulcer.