Dog Loose Stool and Vomiting (What’s Behind It?)

Dog Loose Stool and Vomiting: Common Causes

Dietary Indiscretion

The most common reason for a dog to have loose stool and vomit is simply eating something they shouldn’t have.

Dogs explore with their mouths, and scavenging scraps, spoiled food, or garbage can upset the stomach and intestines. Even a sudden switch to a new food brand can shock the digestive system.

When this happens, the stomach becomes irritated first—causing vomiting—followed by intestinal upset, leading to diarrhea or loose stool.

You may notice your dog licking their lips, drooling, or acting nauseated before vomiting. Once the system clears itself, most dogs bounce back quickly.

However, if diarrhea persists for more than a day or contains mucus or blood, the irritation may have caused inflammation severe enough to require veterinary attention.

Read more: Dog Loose Stool with No Other Symptoms (What it means) 

Bacterial or Viral Infections

Gastrointestinal infections are another frequent culprit. Dogs can contract bacteria like Salmonella or E. coli from contaminated water, raw food, or feces. Viral infections such as parvovirus or coronavirus can also attack the intestinal lining, leading to repeated vomiting and loose stool.

Infections inflame the digestive tract and cause fluid loss, making stool watery and foul-smelling. Vomiting often follows as the stomach attempts to remove bacteria or toxins.

Dogs with infections may also act lethargic, run a fever, or refuse food. Puppies, unvaccinated dogs, and those with weak immune systems are especially at risk of severe dehydration.

Because bacterial and viral causes are contagious, isolate your dog from others and disinfect any areas where they’ve vomited or defecated until your vet rules out infection.

Intestinal Parasites

Roundworms, hookworms, whipworms, and giardia can cause chronic loose stool and intermittent vomiting. These parasites irritate the intestines and steal nutrients, leading to poor digestion and inflammation.

If your dog’s stool looks greasy, contains mucus, or has visible worm segments, parasites are likely to blame. Some dogs also lose weight, develop bloated bellies, or scoot due to itching.

Puppies are especially vulnerable, but adult dogs can become infected by drinking from puddles, eating contaminated soil, or catching fleas carrying tapeworm eggs.

Veterinarians can confirm the diagnosis with a fecal test and prescribe dewormers or antiparasitic medication.

Dietary Intolerances

Some dogs are sensitive to specific proteins, grains, or additives in their diet. When a dog with food sensitivities eats the wrong ingredient, the immune system reacts with inflammation in the gut. This triggers loose stool, vomiting, gas, and sometimes chronic itching or ear infections.

Common allergens include chicken, beef, dairy, wheat, and soy. The vomiting occurs because the stomach reacts to the allergen, while diarrhea follows as the intestines struggle to process the irritant.

If you suspect food intolerance, try feeding a bland or hypoallergenic diet for several weeks.

Improvement during this period can help your vet identify the trigger ingredient through a formal elimination diet.

Pancreatitis

Pancreatitis—an inflammation of the pancreas—is a painful and potentially serious condition that often causes both vomiting and diarrhea. It’s typically triggered by fatty meals, table scraps, or high-fat treats that overwhelm the pancreas.

When the pancreas becomes inflamed, digestive enzymes activate too early, irritating nearby tissues. This leads to nausea, abdominal pain, loss of appetite, and greasy or yellowish loose stool. Vomiting may occur repeatedly, sometimes accompanied by fever or lethargy.

Small breeds like Miniature Schnauzers, Yorkshire Terriers, and Dachshunds are particularly prone to pancreatitis.

Dogs with chronic cases may need lifelong dietary management on a low-fat diet to prevent recurrences.

Ingestion of Toxins and Foreign Objects

If your dog eats something toxic—like spoiled food, garbage, certain plants, medications, or chemicals—vomiting and diarrhea are immediate defenses. The body tries to purge the toxin through both the stomach and intestines.

Foamy or bloody vomit, dark stool, tremors, or drooling are red-flag signs of poisoning.

Even ingesting inedible objects like toys, socks, or bones can cause obstruction that leads to vomiting, followed by diarrhea when the intestines struggle to move material along.

If your dog continues to vomit after eating or drinking nothing, or if stool turns black, it’s critical to get emergency care—an intestinal blockage or toxin exposure can become life-threatening within hours.

Stress 

Emotional stress can upset a dog’s digestive system just as it can in humans. Travel, boarding, loud noises, or changes at home can cause temporary nausea and diarrhea.

Stress triggers hormonal changes that speed up gut movement and reduce blood flow to the stomach, resulting in loose stool and vomiting. Dogs under stress may pace, tremble, or lick their lips excessively before symptoms appear.

If your dog’s vomiting and diarrhea occur after stressful events but resolve within a day, the cause is likely emotional rather than physical. However, repeated stress-related episodes can weaken the digestive system over time.

Chronic Digestive Disorders

If your dog regularly suffers from vomiting and loose stool, chronic conditions like inflammatory bowel disease (IBD), liver disease, or kidney dysfunction could be the cause.

In IBD, the intestines become chronically inflamed, leading to poor absorption of nutrients and frequent digestive upset. Dogs with liver or kidney disease may also vomit bile or develop loose stool as toxins accumulate in the bloodstream.

Chronic issues usually develop gradually, with periodic flare-ups. Over time, dogs may lose weight, become lethargic, and develop poor coat quality.

These conditions require ongoing veterinary care and special diets to manage inflammation and maintain hydration.

Read more: Dog Has Loose Stool and Throwing Up White Foam  (Here’s why)

What to Do if Your Dog Has Loose Stool and Vomiting

Start by removing food for about 8–12 hours to let your dog’s stomach settle. During this fasting period, make sure fresh water is always available, or offer ice chips to prevent dehydration.

After the rest period, reintroduce small, bland meals such as boiled chicken and plain rice. Feed small portions every few hours instead of one large meal. If vomiting stops and stool begins to firm up, gradually transition back to regular food over the next couple of days.

Keep a close eye on your dog’s hydration. Gently lift the skin on the back of the neck—it should snap back quickly. If it stays tented or your dog’s gums appear dry and tacky, dehydration may already be developing.

Avoid giving over-the-counter human medications like Pepto-Bismol or Imodium unless directed by your vet. These can mask symptoms or worsen certain conditions.

If vomiting or diarrhea persists beyond 24 hours—or if other symptoms appear—your dog needs veterinary evaluation.

When to Call or Visit the Vet

Call your vet right away if your dog:

• Vomits repeatedly or can’t keep water down.
• Has diarrhea lasting more than 24–36 hours.
• Passes stool with blood, mucus, or a black tar-like color.
• Seems weak, lethargic, or collapses.
• Shows signs of abdominal pain or bloating.
• Refuses to eat or drink.
• Has a fever, pale gums, or sunken eyes.
• Recently ate garbage, bones, toys, or toxic plants.
• Is a young puppy, senior, or has chronic health issues.

Seek emergency care immediately if vomiting and diarrhea are accompanied by severe lethargy, collapse, or a distended abdomen—these could indicate poisoning, pancreatitis, or intestinal blockage.

Read more: Dog Loose Stool and Vomiting Bile (What it means)

Key Takeaway

Dog loose stool and vomiting can range from mild stomach upset to signs of infection or pancreatitis. While short episodes after dietary mistakes may resolve at home, persistent symptoms or blood in the stool always warrant professional attention.

The sooner you identify the cause, the faster your dog can recover—with proper hydration, a gentle diet, and veterinary guidance to prevent recurrence.