What causes ulcers

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Last updated: April 4, 2026

Quick Answer: The primary causes of stomach and duodenal ulcers are infections with the bacterium *Helicobacter pylori* (H. pylori) and long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs). While stress and spicy foods don't directly cause ulcers, they can worsen symptoms.

Key Facts

What Causes Stomach and Duodenal Ulcers?

Ulcers, also known as peptic ulcers, are open sores that develop on the lining of the stomach or the upper part of the small intestine, called the duodenum. For decades, the exact causes of these painful conditions were debated, with common misconceptions pointing to stress and diet. However, modern medicine has identified two main culprits that are responsible for the vast majority of ulcer cases: infection with a specific bacterium and the use of certain medications.

The Role of *Helicobacter pylori* (H. pylori)

*Helicobacter pylori* (H. pylori) is a type of bacteria that infects the stomach and duodenum. It is estimated that about half of the world's population carries H. pylori, though not everyone infected develops ulcers. This bacterium can survive in the harsh, acidic environment of the stomach by producing an enzyme that neutralizes stomach acid. Over time, H. pylori can damage the protective mucus lining of the stomach and duodenum, making the underlying tissue vulnerable to the corrosive effects of stomach acid, leading to the formation of ulcers.

The transmission of H. pylori is not fully understood, but it is believed to spread through contaminated food or water, or direct contact with saliva, vomit, or fecal matter from an infected person. Poor sanitation and hygiene are significant risk factors for H. pylori infection. In many developing countries, the prevalence of H. pylori infection is much higher than in industrialized nations.

When H. pylori causes an ulcer, it often leads to symptoms such as a gnawing or burning pain in the abdomen, bloating, nausea, and loss of appetite. If left untreated, H. pylori infections can also increase the risk of stomach cancer.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

Another major cause of peptic ulcers is the long-term or frequent use of nonsteroidal anti-inflammatory drugs (NSAIDs). This class of medications, which includes common over-the-counter drugs like ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin, is widely used to relieve pain, reduce inflammation, and lower fever.

NSAIDs work by inhibiting enzymes called cyclooxygenase (COX) enzymes, which play a role in producing prostaglandins. Prostaglandins are substances that help protect the stomach lining from acid. By reducing the production of prostaglandins, NSAIDs can weaken the stomach's natural defenses, making it more susceptible to damage from stomach acid. This can lead to the development of ulcers, particularly in the stomach and duodenum.

The risk of developing an NSAID-induced ulcer is higher in individuals who:

Symptoms of NSAID-induced ulcers are similar to those caused by H. pylori infection.

Other Contributing Factors

While H. pylori and NSAIDs are the primary causes, several other factors can increase your risk of developing ulcers or interfere with their healing:

Smoking

Smoking tobacco significantly increases the risk of peptic ulcers and can slow down the healing process. Nicotine in cigarettes can reduce the blood flow to the stomach lining and stimulate acid production, making the stomach more vulnerable.

Alcohol Consumption

Excessive consumption of alcohol can irritate and erode the stomach lining. While moderate alcohol intake might not directly cause ulcers, heavy drinking can exacerbate existing ulcers or increase the likelihood of developing new ones.

Severe Stress

Although severe emotional stress or worry doesn't directly cause ulcers, it can worsen existing ulcer symptoms. In the past, stress was widely believed to be a primary cause, but research has shown it's more of an aggravating factor than a direct cause. However, physiological stress from serious illness or surgery can sometimes contribute to ulcer formation.

Genetics

There may be a genetic predisposition to developing ulcers. Individuals whose close family members have a history of ulcers may be at a slightly higher risk.

Misconceptions About Ulcer Causes

It's important to address common myths:

Diagnosis and Treatment

If you suspect you have an ulcer, it's crucial to consult a healthcare professional. Diagnosis often involves a physical examination, discussion of your symptoms and medical history, and tests such as endoscopy (a procedure where a flexible tube with a camera is inserted into the digestive tract) or tests for H. pylori infection. Treatment typically involves eradicating H. pylori with antibiotics, reducing stomach acid production with medications like proton pump inhibitors (PPIs), and discontinuing NSAIDs if possible. Lifestyle modifications, such as quitting smoking and limiting alcohol, are also essential for healing and preventing recurrence.

Sources

  1. Peptic ulcer - WikipediaCC-BY-SA-4.0
  2. Ulcers - Symptoms and causes - Mayo Clinicfair-use
  3. Stomach (gastric) ulcers - NHSfair-use

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