Gastritis in dogs, or inflammation of the stomach lining, is most commonly caused by dietary indiscretion: eating something they shouldn’t have. But the list of triggers goes well beyond a raided trash can. Medications, toxins, underlying diseases, and even the dog’s own immune response can all damage the protective barrier that keeps stomach acid from injuring the stomach wall.
How the Stomach Lining Breaks Down
A dog’s stomach is built to handle its own acid. Seven protective factors work together to form what’s called the gastric mucosal barrier: a layer of water-repelling mucus, bicarbonate secretion that neutralizes acid near the surface, rapid replacement of damaged cells, strong blood flow to the stomach wall, and the production of protective compounds called prostaglandins. When any of these defenses weaken, trouble starts fast.
Once the barrier is compromised, stomach acid and digestive enzymes begin seeping backward into the exposed tissue. This triggers a chain reaction. Inflammatory cells flood the area and release chemicals that cause swelling, increased acid production, and damage to tiny blood vessels. Blood flow drops, which means the stomach can’t replace injured cells or produce enough protective mucus. The initial damage feeds on itself, making the inflammation progressively worse.
Dietary Indiscretion
This is the single most common cause of acute gastritis in dogs. It covers a wide range of scenarios: getting into the garbage, eating spoiled or contaminated food, swallowing foreign objects like toys or fabric, or simply eating a new food their stomach isn’t used to. Dogs are opportunistic eaters, and their willingness to consume nearly anything regularly lands them in trouble. Fatty table scraps are a particularly frequent offender because high-fat foods are harder to digest and more irritating to the stomach lining.
Foreign objects deserve special attention. A dog that swallows a sock, a piece of bone, or a chunk of plastic can develop gastritis from the physical irritation alone, even if the object doesn’t cause a full blockage. If you notice your dog vomiting repeatedly after getting into something they shouldn’t have, the cause is often straightforward, but persistent vomiting or signs of pain warrant a closer look to rule out an obstruction.
Medications That Damage the Stomach
Anti-inflammatory drugs (NSAIDs) are one of the most well-documented causes of gastritis in dogs. These medications damage the stomach in two distinct ways. First, they have a direct topical effect: because NSAIDs are weak acids, they can pass through stomach cell membranes and release hydrogen ions inside the cells, disrupting normal cell function. They also strip away the water-repelling quality of the mucus layer, leaving the tissue underneath exposed to acid.
The second mechanism is systemic. NSAIDs block the production of prostaglandins, which are essential for maintaining blood flow to the stomach lining, stimulating mucus and bicarbonate production, and driving the rapid cell turnover that repairs everyday wear. When prostaglandin levels drop, every major defense in the stomach weakens simultaneously. This is why even a short course of an NSAID can cause stomach irritation in some dogs, and why giving human NSAIDs like ibuprofen to a dog is dangerous.
Corticosteroids, commonly prescribed for allergies and autoimmune conditions, can also predispose dogs to gastritis. They reduce mucus production, alter the chemical makeup of the mucus that is produced, slow down the replacement of surface cells, and increase acid output. Dogs on long-term steroids or those receiving steroids alongside NSAIDs are at significantly higher risk.
Toxins, Plants, and Chemicals
A variety of household and environmental substances can inflame a dog’s stomach. Common culprits include certain houseplants, cleaning chemicals, fertilizers, and pesticides. Some of these cause direct chemical burns to the stomach lining, while others trigger inflammation after being absorbed into the bloodstream. If your dog has access to a garage, garden shed, or areas with treated lawns, these exposures are worth considering any time unexplained vomiting develops.
The Helicobacter Question
In humans, Helicobacter bacteria are a major cause of stomach ulcers and gastritis. Naturally, pet owners wonder if the same applies to dogs. The answer is surprisingly unclear. Nearly all dogs carry Helicobacter species in their stomachs, whether they have symptoms or not. Studies consistently find the bacteria at similar rates in healthy dogs and dogs with gastrointestinal problems, which makes it difficult to pin gastritis on the infection alone.
The current veterinary consensus leans toward viewing these bacteria more as normal residents of the canine stomach than as true pathogens. When gastritis does develop in an infected dog, it may be less about the bacteria being harmful and more about the dog’s immune system losing its tolerance to organisms it normally coexists with peacefully. This is a meaningful distinction: it means treating the bacteria with antibiotics doesn’t reliably resolve the gastritis, and testing positive for Helicobacter doesn’t necessarily explain a dog’s symptoms.
Underlying Diseases
Gastritis sometimes develops as a secondary problem, driven by disease elsewhere in the body. Kidney disease is a classic example. When the kidneys can no longer filter waste products effectively, toxins build up in the blood and can irritate the stomach lining. That said, full-blown stomach ulceration from kidney failure is less common in dogs than many owners expect. Liver disease, inflammatory bowel disease, and certain cancers can also produce chronic stomach inflammation.
Immune-mediated conditions, where the dog’s own immune system attacks the stomach lining, are another category. These tend to cause chronic gastritis that doesn’t respond to the usual dietary changes. They’re less common than dietary or medication-related causes but important to consider when a dog has persistent, unexplained vomiting over weeks or months.
Acute vs. Chronic Gastritis
The distinction matters because the causes, severity, and outlook are quite different. Acute gastritis comes on suddenly, usually within hours of the trigger. A dog that ate garbage yesterday and is vomiting today has acute gastritis. It’s typically self-limiting, meaning it resolves once the offending substance clears the system, often within one to three days.
Chronic gastritis is persistent or recurring inflammation lasting weeks or longer. The causes tend to be subtler: food sensitivities, ongoing medication use, immune-mediated disease, or an undiagnosed systemic illness. Because chronic gastritis doesn’t resolve on its own, it usually requires diagnostic workup. Endoscopy, where a small camera is passed into the stomach, allows a veterinarian to visualize the lining directly and take tissue samples. Biopsy results can distinguish between different types of inflammation (lymphocytic, eosinophilic, or atrophic, for instance), which points toward the underlying cause and guides treatment.
What Recovery Looks Like
For acute gastritis, management focuses on letting the stomach heal while keeping the dog nourished. The old advice of fasting a dog for 24 to 48 hours has fallen out of favor. Veterinary understanding has shifted: the stomach lining actually needs nutrients to repair itself, and withholding food can delay healing and cause additional damage to the gut.
A bland, easily digestible diet is still the cornerstone of recovery, but the classic boiled chicken and white rice combination isn’t the best option either. That mix is deficient in more than ten essential nutrients for dogs, making it a poor choice for anything beyond a single meal. Commercially prepared gastrointestinal diets are now preferred because they’re nutritionally complete while still being gentle on the stomach. Your vet can recommend a specific product based on your dog’s size and needs.
When gastritis is caused by a medication, stopping or switching the drug (under veterinary guidance) is the most important step. For chronic cases tied to immune-mediated disease or food sensitivities, treatment is longer-term and may involve dietary trials with novel protein or hydrolyzed diets to identify triggers. Recovery timelines in chronic gastritis are measured in weeks to months rather than days.