Most stomach and duodenal ulcers are caused by one of two things: a bacterial infection called H. pylori or regular use of common pain relievers like ibuprofen and naproxen. Together, these two causes account for the vast majority of peptic ulcers. Other factors, from smoking and alcohol to rare tumor conditions, can also trigger or worsen them. The idea that spicy food or everyday stress causes ulcers is largely a myth.
H. pylori: The Most Common Cause
Helicobacter pylori is a spiral-shaped bacterium that colonizes the stomach lining, sometimes for decades without causing symptoms. Roughly half the world’s population carries H. pylori, but only a fraction develop ulcers. People infected with the bacterium develop peptic ulcers at a rate about six to ten times higher than uninfected people.
What makes H. pylori remarkable is how it survives in one of the most acidic environments in the body. The bacterium produces an enzyme called urease that breaks down urea into ammonia and carbon dioxide. The ammonia neutralizes the acid immediately surrounding the bacterium, creating a small pocket of near-neutral pH that lets it thrive. Meanwhile, that same ammonia damages the stomach lining by disrupting the tight junctions between cells, essentially punching holes in the protective barrier. Once that barrier is compromised, stomach acid reaches the delicate tissue underneath and begins eroding it into an open sore.
H. pylori infection is typically picked up in childhood and persists unless treated. A combination of antibiotics and acid-reducing medication clears it in most cases, and once it’s gone, the ulcer usually heals and doesn’t come back.
Pain Relievers That Damage the Stomach Lining
Non-steroidal anti-inflammatory drugs, better known as NSAIDs, are the second leading cause of peptic ulcers. This group includes over-the-counter staples like ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin, along with prescription options. These medications work by blocking an enzyme involved in inflammation, but that same enzyme also helps produce a protective mucus layer in the stomach. When that mucus thins out, acid can eat into the exposed tissue.
Not all NSAIDs carry the same risk. Ibuprofen and celecoxib sit at the lower end, with a relative risk of gastrointestinal complications under two times normal. Diclofenac and meloxicam fall in the middle range, roughly two to four times higher risk. Naproxen and indomethacin push the risk to four or five times higher, while piroxicam (7.4 times) and ketorolac (11.5 times) carry the highest risk of any commonly used NSAIDs.
The danger increases with dose, duration, and age. Taking an NSAID occasionally for a headache is very different from taking one daily for chronic arthritis. If you rely on these medications regularly, your doctor can add an acid-reducing drug to protect the stomach lining or switch you to a lower-risk option.
Smoking and Alcohol
Smoking doesn’t just irritate the stomach. It actively undermines the body’s ability to repair mucosal damage. Research shows that cigarette smoking reduces blood flow to the stomach lining, suppresses cell growth needed for tissue repair, increases free radical production, and lowers levels of a growth factor the stomach uses to maintain its protective barrier. The result: smokers develop ulcers more often, heal more slowly, and relapse at higher rates than nonsmokers.
Alcohol damages the stomach lining directly, weakening its structural integrity. Heavy drinking on its own raises ulcer risk, but the combination of alcohol and smoking is particularly harmful. Animal studies confirm that smoking potentiates alcohol-induced damage to the stomach wall, with measurable increases in inflammatory markers and decreases in mucus production. If you drink and smoke together, the risk isn’t simply additive. It’s compounded.
Severe Physical Stress
Everyday psychological stress, like a demanding job or financial worry, does not cause ulcers. But severe physiological stress can. When the body is fighting for survival after major trauma, extensive burns, or brain injury, blood flow gets redirected away from the gut and toward vital organs. The stomach’s protective mechanisms break down, and ulcers can form rapidly.
These stress ulcers are well-documented in intensive care settings. Burns covering more than 30% of the body can produce what’s called a Curling ulcer. Traumatic brain injury can trigger a Cushing ulcer, driven by a surge in acid production. Patients on mechanical ventilation for more than 48 hours, those in septic shock, and people with liver or kidney failure also face elevated risk. These aren’t the kind of ulcers most people searching this topic will encounter, but they explain why “stress causes ulcers” became a widespread belief. The stress involved is life-threatening, not the daily kind.
A Rare but Serious Cause: Gastrinomas
In uncommon cases, a tumor called a gastrinoma produces excessive amounts of a hormone that tells the stomach to make acid. Normally, the stomach has a feedback loop: when acid levels are high enough, the signal to produce more shuts off. Gastrinomas ignore that feedback entirely, flooding the system with the hormone regardless of how much acid is already present. Over time, the relentless acid output overwhelms the stomach’s defenses and causes severe, hard-to-treat ulcers. This condition, known as Zollinger-Ellison syndrome, accounts for a tiny fraction of all peptic ulcers but should be considered when ulcers keep returning despite standard treatment.
Spicy Food Is Not the Culprit
For decades, people with ulcers were told to avoid chili peppers and spicy cuisine. The science tells a different story. Capsaicin, the compound that makes peppers hot, does not stimulate acid secretion. It actually inhibits it. Capsaicin also promotes mucus production and increases blood flow to the stomach lining, both of which help protect against ulcers rather than cause them.
Epidemiological data backs this up. A survey in Singapore found that gastric ulcers were three times more common among Chinese residents than among Malaysian and Indian residents, who consumed significantly more chili. Spicy food may temporarily aggravate symptoms if you already have an ulcer, which is likely where the myth originated. But it doesn’t create one.
What Happens When Ulcers Go Untreated
Most ulcers cause a gnawing or burning pain in the upper abdomen, often between meals or at night when the stomach is empty. Some cause no noticeable symptoms at all. The real danger comes when an ulcer deepens enough to erode into a blood vessel or penetrate the stomach wall entirely.
A bleeding ulcer can cause dark, tarry stools or vomiting that looks like coffee grounds. Slow bleeding over weeks leads to anemia, fatigue, and lightheadedness. A perforated ulcer, where the sore breaks through the stomach or duodenal wall, is a medical emergency. Digestive juices spill into the abdominal cavity, causing intense sudden pain, a rigid abdomen, and rapid heart rate. Within hours, the pain spreads, worsens with any movement, and can progress to dangerously low blood pressure and organ damage if not treated surgically.
Long-standing ulcers can also cause swelling and scarring that narrows the outlet of the stomach, making it difficult for food to pass through. This leads to persistent vomiting, bloating, and unintentional weight loss.
How Ulcers Are Found
If your symptoms suggest an ulcer, the next step is usually testing for H. pylori. This can be done through a breath test, a stool sample, or a blood test. The breath test is particularly straightforward: you swallow a small amount of a harmless substance, and if H. pylori is present, the bacterium’s urease enzyme breaks it down in a way that’s detectable in your breath.
An upper endoscopy, where a thin flexible camera is passed down the throat into the stomach, is the gold standard for confirming an ulcer. It lets a doctor see the ulcer directly, assess its severity, and take tissue samples if needed. Endoscopy is especially important when there are warning signs like bleeding, significant weight loss, or symptoms that don’t respond to initial treatment. For active bleeding ulcers, endoscopy doubles as treatment, allowing the doctor to seal the bleeding site during the same procedure.