Stomach ulcers are open sores that develop in the lining of the stomach or upper small intestine when the protective mucus barrier breaks down and acid eats into the tissue beneath. The two most common causes are infection with a specific bacterium and regular use of common pain relievers. Peptic ulcer disease affects roughly 10 to 15% of people worldwide, with duodenal ulcers (in the upper intestine) making up 19 out of every 20 cases.
How the Stomach’s Defense Breaks Down
Your stomach produces strong acid to digest food, but a thick, tightly adhering layer of mucus normally keeps that acid from touching the stomach wall itself. This mucus barrier is your first line of defense. When something damages it, whether an infection or a chemical irritant, acid reaches the exposed tissue and begins to erode it. If the damage outpaces your body’s ability to repair the lining, an ulcer forms.
H. pylori Infection
The bacterium Helicobacter pylori is the single most common cause of stomach ulcers worldwide. It burrows into the mucus layer and triggers chronic inflammation that weakens the stomach’s protective barrier. Many people carry H. pylori without ever developing symptoms, but in a significant percentage, the ongoing inflammation eventually allows acid to damage the underlying tissue. The infection spreads through contaminated water, food, or close person-to-person contact, which is why ulcer rates remain highest in South Asia and Western Sub-Saharan Africa, regions where sanitation infrastructure is less developed.
H. pylori infection is treatable with a course of antibiotics combined with acid-reducing medication. Once the bacterium is eliminated, the ulcer typically heals and the risk of recurrence drops sharply.
Pain Relievers and Anti-Inflammatory Drugs
Nonsteroidal anti-inflammatory drugs, commonly called NSAIDs, are the other major cause. This category includes ibuprofen, naproxen, and aspirin. These medications are fat-soluble, which means they easily pass through the membranes of stomach lining cells. Once inside, the drug molecules become trapped and draw water into the cell through osmosis, eventually causing the cell to burst. That direct toxic effect, combined with NSAIDs’ ability to suppress the production of protective compounds in the stomach wall, creates a recipe for ulceration.
Duration of use matters more than any single dose. Research shows that continuous NSAID use beyond 30 days significantly raises ulcer risk, while shorter courses do not appear to carry the same danger. Risk also climbs with higher cumulative doses. People who need long-term pain management with these drugs are often prescribed an acid-reducing medication alongside them to protect the stomach lining.
Smoking and Alcohol
Neither smoking nor heavy alcohol use causes ulcers on its own in the way H. pylori or NSAIDs do, but both make ulcers more likely to form and harder to heal. Cigarette smoke reduces blood flow to the stomach lining and slows the growth of new blood vessels at the site of an existing ulcer. In animal studies, smoke exposure significantly delayed ulcer healing by suppressing the production of nitric oxide, a molecule the body uses to maintain healthy blood flow in the stomach wall. The practical result: smokers with ulcers heal more slowly and relapse more often.
Alcohol in large quantities can erode the mucus layer directly, leaving the tissue underneath vulnerable to acid. Moderate drinking has not been clearly linked to ulcer formation, but heavy or binge drinking compounds the risk, especially when combined with NSAID use or an existing H. pylori infection.
Severe Physical Stress
The kind of stress that causes ulcers is not the everyday work-deadline variety. Ulcers linked to physical stress develop in people who are critically ill: those recovering from major surgery, severe burns, traumatic injuries, or organ failure. In these situations, blood flow to the stomach drops dramatically as the body redirects resources to vital organs, and the protective lining deteriorates rapidly. These stress ulcers can develop within days of a critical illness and are a recognized complication in intensive care settings.
Everyday psychological stress does not directly cause ulcers, though people diagnosed with ulcers frequently report high levels of daily stress. The likely explanation is that stress drives behaviors that do raise risk, like smoking, drinking, skipping meals, or relying heavily on over-the-counter pain relievers.
Rare Causes Worth Knowing
A small number of ulcers stem from a condition called Zollinger-Ellison syndrome, in which tumors called gastrinomas form in the pancreas or upper small intestine. These tumors release massive amounts of gastrin, a hormone that signals the stomach to produce acid. Normally, your body releases a small burst of gastrin after a meal. Gastrinomas flood the system with it continuously, driving acid production far beyond what the mucus barrier can handle. The result is severe, often multiple ulcers that resist standard treatment. Doctors diagnose the condition through a fasting blood test that measures gastrin levels.
Age and Sex Differences
Ulcer risk rises with age, particularly after 60. Older adults are more likely to use NSAIDs for joint pain and arthritis, and the stomach lining naturally thins over time, making it more vulnerable. Men face a notably higher burden than women: males aged 45 to 49 have a prevalence rate 1.4 times higher than females in the same age group, and their mortality rate from ulcer complications is 2.2 times higher.
Spicy Food Does Not Cause Ulcers
For decades, doctors told ulcer patients to eat bland diets. That advice has been retired. No large-scale studies have found a positive association between spicy food consumption and ulcer formation, and the American College of Gastroenterology no longer recommends bland diets for people with peptic ulcer disease. Capsaicin, the compound that gives chili peppers their heat, may actually support healing by reducing acid secretion and promoting the production of protective mucus. That said, spicy foods can aggravate symptoms like burning or discomfort in people who already have an ulcer, so avoiding them during a flare-up is reasonable.
Warning Signs of Complications
Most ulcers cause a gnawing or burning pain in the upper abdomen, often between meals or at night when the stomach is empty. That pain is uncomfortable but manageable. The danger comes when an ulcer erodes into a blood vessel or penetrates entirely through the stomach wall. Signs that an ulcer has become a medical emergency include vomiting blood (which may look bright red or resemble dark coffee grounds), black or tarry stools (a sign of bleeding in the digestive tract), sudden sharp abdominal pain that doesn’t let up, and unexplained weight loss or inability to keep food down. A perforated ulcer, one that has broken through the stomach wall, causes sudden, severe pain and requires immediate surgical attention.