Nothing prompts pet owners to call Homestead Animal Hospital faster than diarrhea—and with good reason. Diarrhea is one of the most unpleasant clinical signs for pets and their people and, more importantly, its presence can signal a serious underlying health issue. Whether your pet’s messes are sudden or chronic, minor or major, contained or explosive—we are here to help. Check out these common reasons why pets get diarrhea, and then schedule an appointment at Homestead Animal Hospital.

What is diarrhea in pets?

We know it when we see it—or smell it—but what is diarrhea, and why does it happen? Diarrhea is generally defined as loose or unformed stool occurring with higher frequency or in larger volume than your pet’s normal bowel movements. Diarrhea happens when your dog’s intestinal contents move through the small and large intestine (i.e., colon) faster than usual, which prevents the normal absorption of fluids, electrolytes, and nutrients that helps solidify stool. This is also why diarrhea can cause rapid dehydration and weakness.

Depending on the cause, diarrhea in dogs can range from semi-soft to watery, be abnormally colored (e.g., green, yellow, or black), or contain blood or mucus.

Is diarrhea always serious in pets?

While some diarrhea is self-limiting and resolves in 24 hours, the Homestead Animal Hospital team advises pet owners to schedule an appointment in the following situations:

  • Additional signs are present — Diagnostic testing and treatment is necessary if your dog also is lethargic, vomiting, or refusing to eat.
  • Your dog is a puppy — Viral diseases and parasites are common diarrhea causes in young pets and can result in severe dehydration, anemia, and death.
  • Your dog is a senior — Aging pets with diarrhea may have an underlying disease, and like young pets, can experience rapid dehydration and require hospitalization.
  • Persistent diarrhea — Persistent diarrhea that lasts more than 24 to 48 hours, or chronic diarrhea that seems to come and go, require veterinary attention.
  • Bloody diarrhea — Depending on the location of your pet’s intestinal inflammation, blood in the stool may appear black or bright red, or resemble coffee grounds.

What causes diarrhea in dogs?

Gastrointestinal distress and diarrhea in dogs have literally hundreds of causes. We’ve narrowed the list to the most common causes that we see in our Homestead Animal Hospital patients.

  • Stress  Stress and anxiety can negatively impact a pet’s digestion. Stress colitis is intestinal inflammation triggered by physical or emotional stress that reduces your pet’s immunity, disrupts gut flora, and results in diarrhea. Stress colitis is most frequently associated with pet hospitalization, relocation, home environment changes, frightening events (e.g, fireworks, thunderstorms), or being boarded. 
  • Dietary indiscretions — Some pets eat everything—including inappropriate food they find in the trash can and inedible objects. When these items reach the digestive tract, their foreign composition upsets the GI tract and results in inflammation, irritation, or in some cases, a partial or complete GI blockage that requires surgery. Dogs find rich human foods containing high fat, salt, or sugar content difficult to digest, and these foods commonly cause pancreatitis and diarrhea. 
  • Infectious diseases — Diarrhea in puppies and unvaccinated dogs is always a cause for concern. Life-threatening contagious viruses, including canine parvovirus and distemper, can wreak havoc on a dog’s gastrointestinal tract and immune system, resulting in diarrhea, vomiting, and a severe and rapid decline. Fortunately, vaccines provide reliable protection against these deadly threats, so ensure your puppy or dog stays current on their vaccinations.
  • Intestinal parasites — When your pet has diarrhea, we’ll perform a fecal screening to look for intestinal parasites, such as roundworms, whipworms, coccidia, and giardia. These parasites irritate the intestines by biting and feeding or invading the tissue, triggering inflammation and diarrhea. Roundworms, whipworms, and coccidia, which are transmitted through infected pet waste, are most common in puppies. Giardia infection can occur in a dog after exposure to a contaminated water source.
  • Food allergy or intolerance — Contrary to popular belief, food allergies and sensitivities in pets are most often in response to protein, rather than carbohydrates or grain. Food allergies can develop at any time in a pet’s life—including after eating the same food for many years with no problems. When a pet has a food allergy, their body reacts to the allergen with inflammation. Chronic food allergy diarrhea may be accompanied by vomiting, but usually can be resolved by feeding the pet a strict hypoallergenic or novel protein diet.
  • Inflammatory bowel disease— Inflammatory bowel disease (IBD) stems from a variety of causes—some still unknown—but is defined by an accumulation of inflammatory cells in the stomach, small intestine, or large intestine lining. Pets with IBD experience chronic diarrhea and vomiting, and weight loss. If the IBD affects the large intestine, the diarrhea may contain blood or mucus, and pets may experience an increased urgency and strain to defecate. IBD diagnosis involves lab work, imaging, and an intestinal biopsy to ensure effective treatment.
  • Toxin ingestion — Numerous pet toxins can trigger diarrhea, including chocolate, medications, toxic plants, alcohol, dairy products, avocados, and insecticides. If you know or suspect your pet has consumed something toxic, don’t wait until clinical signs appear—immediately contact Homestead Animal Hospital or call the ASPCA Animal Poison Control Center for after-hours guidance. 

How can I treat my pet’s diarrhea?

Mildly affected dogs who don’t meet the criteria for urgent veterinary attention may be monitored at home and fed a low-fat bland diet, such as boiled chicken or hamburger and white rice.

However, if your dog’s diarrhea persists longer than 24 to 48 hours, comes and goes over several weeks, or is accompanied by other clinical signs, contact Homestead Animal Hospital for prompt veterinary care.