Acute gastritis is a sudden inflammation of the stomach lining that causes burning or gnawing pain in the upper abdomen. Unlike chronic gastritis, which develops gradually over months or years, the acute form comes on quickly and is usually tied to a specific trigger: a medication, an infection, or heavy alcohol use. Most cases resolve once the trigger is removed, but left untreated, acute gastritis can progress to bleeding ulcers or longer-lasting damage.
What Causes It
Three culprits account for the vast majority of acute gastritis cases. The most common worldwide is infection with H. pylori, a bacterium that burrows into the stomach’s protective mucus layer. Once established, it triggers a flood of immune cells, particularly neutrophils, into the stomach lining. The bacterium also releases enzymes that draw even more immune cells to the site, while the stomach’s own tissue ramps up production of inflammatory signaling molecules. The result is rapid, widespread irritation of the inner stomach wall.
Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, aspirin, and naproxen are the second major cause. These medications work by blocking an enzyme involved in pain signaling, but that same enzyme is responsible for producing compounds that keep the stomach lining intact. Without those protective compounds, the mucus barrier thins, tight junctions between cells loosen, and stomach acid reaches tissue it normally never touches. The damage can start within days of regular NSAID use.
Alcohol is the third common trigger. It directly irritates the mucous lining of the stomach, and heavy or binge drinking can cause inflammation severe enough to produce symptoms within hours. Less common causes include severe physical stress (major surgery, burns, critical illness), bile reflux, and cocaine use.
How It Feels
The hallmark symptom is a gnawing or burning pain in the upper belly, roughly in the area between your lower ribs. This pain may get worse after eating, or in some people, it temporarily improves with food before returning. Other common symptoms include nausea, vomiting, a feeling of fullness in the upper abdomen after eating only a small amount, and loss of appetite.
Some people with acute gastritis have no noticeable symptoms at all, especially early on. The inflammation is there, but it hasn’t progressed enough to cause pain. This is one reason the condition sometimes goes undetected until it causes complications.
When It Becomes Dangerous
The main risk of untreated acute gastritis is erosion of the stomach lining deep enough to cause bleeding. If the inflammation eats through the mucosa and damages blood vessels underneath, you can develop a bleeding ulcer. Signs that this has happened include black or tarry stools, vomit that looks like coffee grounds or contains red blood, cramping abdominal pain, and feeling unusually tired, light-headed, or short of breath. These symptoms warrant immediate medical attention.
Mild bleeding can also occur without obvious signs. Small amounts of blood may mix into stool without changing its appearance, a situation called occult bleeding. Over time, this slow blood loss can lead to iron-deficiency anemia, causing fatigue and weakness that seem unrelated to the stomach.
How Acute Gastritis Differs From Chronic
The distinction isn’t just about timing. Under a microscope, acute and chronic gastritis look fundamentally different. Acute gastritis is characterized by a surge of neutrophils, the immune system’s first responders, flooding into the stomach lining. Pathologists actually grade the severity of gastritis by how deep these neutrophils penetrate: cells in the surrounding tissue indicate mild activity, cells that have invaded the lining itself indicate moderate activity, and cells that have reached the gland openings indicate marked activity.
Chronic gastritis, by contrast, shows a different immune profile dominated by lymphocytes and plasma cells, the slower-acting, long-term players of the immune system. Over time, chronic inflammation leads to atrophy, where the acid-producing glands of the stomach gradually shrink and disappear. Acute gastritis doesn’t typically cause this kind of structural change, which is why it’s generally reversible if caught and treated early. However, untreated acute H. pylori gastritis frequently transitions into chronic gastritis over months.
How It’s Diagnosed
A doctor will typically start with your symptom history and a physical exam. If acute gastritis is suspected, the most definitive test is an upper GI endoscopy: a thin, flexible tube with a camera is passed through the mouth and into the stomach, giving a direct view of the lining. During this procedure, the doctor can take small tissue samples (biopsies) from areas that look inflamed or damaged. A pathologist then examines these samples under a microscope to confirm inflammation, identify the type of immune cells present, and check for H. pylori bacteria.
Not everyone with suspected gastritis needs an endoscopy. For younger patients with straightforward symptoms and an obvious trigger like NSAID use, a doctor may start treatment based on the clinical picture alone and reserve endoscopy for cases that don’t improve or that raise concern about complications.
Treatment and Recovery
The first step is removing whatever caused the inflammation. If NSAIDs are the culprit, stopping them or switching to a different type of pain reliever (like acetaminophen) is often enough for the stomach to begin healing. If alcohol is the trigger, stopping drinking allows the lining to recover.
For H. pylori infections, treatment involves a combination of antibiotics to eliminate the bacteria. This is paired with an acid-reducing medication, most commonly a proton pump inhibitor (PPI), which dramatically lowers stomach acid production to give the inflamed tissue a chance to heal. PPIs are also used on their own when the gastritis isn’t caused by H. pylori but the stomach lining still needs time to recover. Standard courses typically run a few weeks, though the duration depends on severity.
Most cases of acute gastritis improve significantly within days to weeks once the cause is addressed. Erosive gastritis caused by NSAIDs or alcohol tends to heal relatively quickly after the offending substance is removed, especially with acid suppression. H. pylori-related gastritis takes longer because the antibiotic regimen itself requires time, and the stomach lining needs additional weeks to fully repair after the infection clears.
What to Eat During Recovery
While your stomach heals, what you eat matters. The general principle is to avoid anything that increases acid production or directly irritates inflamed tissue. That means cutting out spicy foods (chili powder, curry, hot peppers, black and red pepper), acidic foods (citrus fruits, tomatoes and tomato-based sauces), fried and high-fat foods, chocolate, and heavily processed meats like sausage, salami, and bacon.
Beverages deserve special attention because several common drinks are surprisingly irritating to an inflamed stomach. Coffee, both regular and decaffeinated, stimulates acid production. The same goes for caffeinated sodas, green and black tea, citrus juices, and alcohol. Even peppermint and spearmint tea, often thought of as soothing, can worsen gastritis symptoms.
Foods that tend to be well tolerated include low-acid fruits like apples and melons, cooked vegetables such as carrots and pumpkin, whole grains (oatmeal, brown rice, whole-wheat bread), lean proteins like skinless poultry, fish, eggs, and beans, and low-fat dairy. High-fiber foods generally ease symptoms rather than aggravate them. One practical habit that helps: stop eating at least two hours before lying down, since a full stomach in a horizontal position pushes acid toward the already-damaged lining.