Gastritis happens when something damages or weakens the protective mucus lining inside your stomach, allowing digestive acid to inflame the tissue underneath. The most common causes are a bacterial infection called H. pylori, regular use of common pain relievers like ibuprofen or aspirin, and heavy alcohol consumption. Globally, about 518 out of every 100,000 people have gastritis at any given time, with rates highest among adults aged 50 to 69.
H. Pylori: The Most Common Cause Worldwide
The single most frequent cause of chronic gastritis is infection with Helicobacter pylori, a spiral-shaped bacterium that has evolved specifically to survive in your stomach. Most people pick it up during childhood through contaminated food, water, or close contact with an infected person. You can carry it for decades without knowing.
H. pylori uses two main tools to establish itself. First, its corkscrew shape and whip-like flagella let it burrow through the thick mucus layer that normally shields your stomach wall from acid. Second, it produces large amounts of an enzyme called urease, which neutralizes the acid in its immediate surroundings, creating a small pocket of safety where the bacterium can thrive. Once embedded in the mucus, it triggers a chronic inflammatory response. Over months and years, that persistent inflammation can thin the stomach lining, reduce acid production, and in some cases set the stage for more serious changes to the tissue.
Pain Relievers and Anti-Inflammatory Drugs
NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen, aspirin, and naproxen are the second leading cause of gastritis. The problem is built into the way these drugs work. They block an enzyme your body uses to produce prostaglandins, the chemical messengers that trigger pain and inflammation. But one form of that enzyme also produces prostaglandins that maintain the stomach’s protective mucus barrier, stimulate blood flow to the lining, and help repair surface cells. When you take an NSAID, you shut down both the pain signals and the stomach’s self-defense system at the same time.
A single dose rarely causes lasting damage. The risk rises with frequent or long-term use, higher doses, and combining multiple NSAIDs. Taking these medications on an empty stomach or pairing them with alcohol increases the likelihood of irritation. If you rely on NSAIDs regularly for conditions like arthritis, your doctor may recommend taking them alongside a medication that reduces stomach acid production to offset the risk.
Alcohol and Chemical Irritants
Alcohol is a direct irritant to the stomach lining. In small amounts, the mucus barrier can handle the exposure. But regular or heavy drinking overwhelms that defense, and the severity of damage correlates with how long the pattern of excessive consumption has lasted. Alcohol can cause both acute gastritis (a sudden flare after a binge) and chronic gastritis that develops gradually over months or years of steady drinking.
Smoking also contributes by reducing blood flow to the stomach lining and impairing its ability to repair itself. Corrosive substances, whether swallowed accidentally or through occupational exposure, can cause severe acute gastritis as well.
Autoimmune Gastritis
In a less common but important form, your own immune system attacks the acid-producing cells in your stomach. This is autoimmune gastritis, an inherited condition in which the body generates antibodies against the cells (called parietal cells) responsible for making stomach acid and a protein called intrinsic factor. Intrinsic factor is essential for absorbing vitamin B12 from food. Without it, B12 levels drop, potentially leading to a specific type of anemia called pernicious anemia, along with neurological symptoms like numbness, tingling, and difficulty with balance.
Autoimmune gastritis tends to progress slowly. Because stomach acid production declines gradually, symptoms may be subtle for years. It’s more common in people who already have other autoimmune conditions, such as thyroid disease or type 1 diabetes.
Bile Reflux
At the bottom of your stomach, a muscular valve called the pyloric valve controls the flow of partially digested food into the small intestine. Normally, it opens just enough to release tiny amounts of liquefied food (roughly a teaspoon at a time) and stays tight enough to prevent digestive fluids from flowing backward. When this valve doesn’t close properly, bile from the small intestine washes back into the stomach. Bile is alkaline and contains salts that are corrosive to the stomach lining, causing a distinct form of inflammation called bile reflux gastritis. This is especially common after certain stomach surgeries that alter or remove the pyloric valve.
Severe Physical Stress
Gastritis doesn’t always come from something you swallowed. In critically ill patients, severe physiological stress from major surgery, burns, traumatic injury, or organ failure can trigger what’s called stress-related mucosal disease. The mechanism is different from other forms: blood flow to the stomach lining drops sharply as the body redirects resources to vital organs, and the resulting lack of oxygen damages the mucosa from within. This type is almost exclusively seen in intensive care settings and is not the same as the everyday emotional stress most people experience.
That said, chronic psychological stress can worsen existing gastritis or make you more susceptible to it. Stress increases acid production, disrupts sleep and eating patterns, and often leads people toward habits (drinking, smoking, skipping meals, overusing pain relievers) that directly harm the stomach lining.
Foods That Worsen Gastritis
No single food causes gastritis on its own, but certain foods reliably aggravate an already inflamed stomach. Spicy ingredients like red pepper, black pepper, and garlic powder can irritate damaged tissue. Citrus fruits, tomatoes, and other acidic foods promote acid reflux, which bathes an inflamed lining in more acid. Highly processed foods made with refined flour are low in fiber and can slow digestion, worsening symptoms. Fatty and sugary foods also tend to trigger acid reflux.
Caffeine and carbonated drinks increase acid secretion. If you already have gastritis, these don’t cause additional structural damage, but they can make the burning, nausea, and discomfort significantly worse.
Who Is Most at Risk
Gastritis rates are higher in women than in men. Globally, about 574 per 100,000 women have the condition compared to roughly 461 per 100,000 men. The peak age range is 50 to 69, where prevalence more than doubles compared to the general population. Rates are also climbing in lower-income regions, where H. pylori infection is more common and access to clean water and sanitation remains limited.
Your risk increases with age partly because the stomach lining naturally thins over time, and partly because older adults are more likely to use NSAIDs regularly, carry longstanding H. pylori infections, or have autoimmune conditions. A family history of autoimmune disease or stomach cancer also raises your risk profile.
How Gastritis Progresses if Untreated
Acute gastritis often resolves on its own once the irritant is removed. You stop drinking, switch off NSAIDs, or clear an infection, and the lining heals within days to weeks. Chronic gastritis is a different story. Left unchecked, persistent inflammation follows a well-documented path known as the Correa cascade. It begins with superficial, non-atrophic gastritis. Over time, the inflammation destroys the specialized glands in the stomach lining, leading to atrophic gastritis, where the tissue thins and acid production drops.
The next stage involves intestinal metaplasia, where stomach cells are gradually replaced by cells that resemble the lining of the intestine. This is the body’s attempt to adapt to ongoing damage, but it comes with risk. Intestinal metaplasia can progress through stages of increasingly abnormal cell growth (dysplasia) and, in a small percentage of cases, eventually develop into stomach cancer. This progression typically takes years to decades, and not everyone with chronic gastritis moves through every stage. But it underscores why identifying and treating the underlying cause matters, especially for H. pylori infection and autoimmune gastritis, where the inflammation is ongoing and silent.