What causes ulcer

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Last updated: April 4, 2026

Quick Answer: The primary cause of peptic ulcers is infection with the bacterium Helicobacter pylori (H. pylori). Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and aspirin is another common cause. Less frequently, ulcers can be caused by rare tumors that produce stomach acid.

Key Facts

What Causes Ulcers?

Ulcers, specifically peptic ulcers, are open sores that develop on the inside of the stomach and the upper part of the small intestine (duodenum). For many years, the exact cause of these painful sores was a mystery, often attributed to stress or diet. However, scientific advancements have identified the primary culprits and contributing factors.

The Role of Helicobacter pylori (H. pylori)

The most common cause of peptic ulcers, accounting for the vast majority of cases, is infection with a type of bacteria known as Helicobacter pylori (H. pylori). This bacterium is remarkably common, infecting roughly half of the world's population. While many people infected with H. pylori never develop symptoms or ulcers, in some individuals, the bacteria can trigger inflammation in the stomach lining (gastritis). This inflammation weakens the protective mucus layer of the stomach and duodenum, making them more vulnerable to the damaging effects of stomach acid and digestive enzymes. Over time, this can lead to the formation of a sore or ulcer.

H. pylori is thought to be spread through contaminated food or water, or through direct contact with an infected person's saliva or vomit. It's a resilient bacterium that can survive the acidic environment of the stomach by producing enzymes that neutralize acid.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

Another significant cause of peptic ulcers, particularly in individuals not infected with H. pylori, is the long-term or frequent use of nonsteroidal anti-inflammatory drugs (NSAIDs). These medications are widely used to relieve pain, reduce inflammation, and lower fever. Common NSAIDs include:

NSAIDs work by inhibiting enzymes called cyclooxygenase (COX) enzymes, which are involved in producing prostaglandins. Prostaglandins play a crucial role in protecting the stomach lining by increasing mucus production and reducing acid secretion. When these prostaglandins are suppressed by NSAIDs, the stomach lining becomes less protected and more susceptible to damage from stomach acid, potentially leading to ulcer formation. The risk is higher with higher doses, longer duration of use, and in older individuals or those with a history of ulcers.

Stomach Acid

While stomach acid is not a direct cause, it plays a critical role in the development and progression of ulcers. The stomach lining is naturally protected by a thick layer of mucus that acts as a barrier against the corrosive effects of hydrochloric acid and digestive enzymes. When this protective barrier is compromised by H. pylori or NSAIDs, the acid can begin to digest the stomach or duodenal lining itself, leading to an ulcer. In essence, acid is the 'solvent' that eats away at the weakened tissue.

Other Contributing Factors

While H. pylori and NSAIDs are the leading causes, several other factors can increase an individual's risk of developing ulcers or hinder their healing:

Debunking Myths

It's important to note that common beliefs about stress and spicy foods causing ulcers are largely myths. While these factors can exacerbate the pain and discomfort of an existing ulcer, they are not the underlying cause. A proper diagnosis by a healthcare professional is essential to identify the true cause and receive appropriate treatment.

Sources

  1. Peptic ulcer - WikipediaCC-BY-SA-4.0
  2. Peptic ulcer - Diagnosis and treatment - Mayo Clinicfair-use
  3. Stomach (gastric) ulcer - NHSfair-use

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