The first research on the effects of gastric acids on the stomach lining was conducted by American Army Physician William Beaumont (1785-1853). Beaumont studied a young war veteran with an open abdominal wound. The wound did not close, but the patient recovered his strength, giving Beaumont an opportunity to study the digestive process. He noticed that the stomach lining turned red when the patient became upset. This may have contributed to the notion that ulcers were caused by stress.

As indestructible notes, the ulcer is a lesion in the mucous membrane of the stomach. This mucous membrane is the protective barrier that shields the stomach from the strong hydrochloric acid (HCl) that is part of the digestive juices. Since it was generally accepted that stress was the major cause of ulcers, the common remedy was to reduce the stress levels. The symptoms were controlled by prescribing food that caused less release of gastric juices, and by H2 blockers; medication that reduces the acidity of gastric juice. The H2 blockers may actually have aggravated the condition, since the stomach reacts by producing more acid.

In the early 1980's, two Australian researchers, Dr. Barry Marshall and Robin Warren noticed the presence of a spiral bacteria, the Helicobacter pylori in patients with gastritis. This bacterium was not recognized as one of the "normal" occupants of the stomach in healthy people. Dr. Marshall was convinced that this bacterium was the primary cause for ulcers and gastritis, but the medical community was highly skeptical about this notice. Their primary objection was that no foreign bacterium would be able to withstand the acidic environment of the stomach (around pH=2). However, Marshall found that this bacterium had been observed in patients as early as the late 1800's.

Unfortunately, no one believed Dr. Barry Marshall. Thus, Marshall did what only the greatest scientists in history do: He infected himself with the bacterium that causes peptic ulcers. Marshall ingested a large dose of the Helicobacter pylori bacterium to prove his peers that his hypothesis was correct. Indeed, Marshall developed gastritis, and cured himself with a simple dose of antibiotics.

Nowadays, the Helicobacter pylori infection is believed to be the most common infection known in the world; approximately 10% of the population will develop an ulcer at some point in their live, although many carry the bacterium without any harmful consequences. A general successful treatment of the infection is by using antibiotics such as tetracycline and metronidazole. Some doctors claim that the infection can also be controlled by simply regaining the balance of bacteria in the gastrointestinal system (i.e. by only drinking water, and avoiding sugar, juices, milk and coffee).

Note that certain rarer types of ulcers are not caused by an infection with Helicobacter pylori. For instance, the Zollinger-Ellison syndrome, or large quantities of NSAIDs can also cause ulcers. Therefore, always consult a doctor if you feel signs of a potential ulcer.