8 Most Common Causes of Diarrhea in Dogs & Cats [Vet-Approved]

A dog and cat side by side to represent the most common causes of diarrhea in dogs and cats

A pet’s stool contains numerous health clues that can help pet parents know if something is wrong. A pet’s stool can show indications of issues in various systems of the body, as well as the presence of worms in dogs or worms in cats. The frequency of elimination also shows if a dog or cat has a healthy bowel movement. One of the most common symptoms observed by pet parents is diarrhea (i.e. the release of soft or watery stools).

Diarrhea in dogs and cats is a symptom, not a disease in and of itself. This symptom can be caused by a variety of factors, such as the ones we will cover in this complete guide. We will give expert tips on what to do to prevent instances of diarrhea and distinguish the cases that need to be brought to the veterinarian.

What’s in This Guide?

1. Sudden Dietary Changes

Dietary changes, such as transitioning to a new brand of pet food or introducing new ingredients, can often disrupt the digestive system in dogs and cats. 

To prevent diarrhea, gradual transitions between diets and providing a consistent, well-balanced meal plan are advisable, allowing their digestive systems to adjust more smoothly to dietary changes.

Sploot’s veterinarians recommend mixing ¾ of the old food with ¼ of new food for a few days, then progressively changing from the old diet to the new one. This provides a gradual transition over 7-10 days. Remember to consult a veterinarian before a diet change to ensure the new food is a complete, nutritious, and is the best fit for your pet’s unique needs.

Note: Although diarrhea in cats and dogs is expected to happen if their food has not been transitioned gradually, severe diarrhea and/or cases lasting more than 24 hours need pet urgent care.

2. Food Allergies

Just like people, dogs and cats can have food allergies too. In fact, cats and dogs can develop allergies to food that we may see as “normal” food for them; the most common food allergens in dogs and cats include animal proteins such as chicken, beef, seafood, and milk.

Food allergies can lead to gastrointestinal distress and diarrhea in dogs and cats. Along with gastrointestinal symptoms, dogs and cats with allergies can also experience symptoms like vomiting, itchy skin, hair loss, itchy paws, ear infections, and more. 

Note: It is important to note that food allergies can lead to anaphylaxis in some pets, a life-threatening allergic reaction. The symptoms of anaphylaxis include facial swelling, rapid breathing and wheezing, rapid heart rate, and weakness or collapse. If you notice these signs in your pet bring them to an urgent care veterinary clinic or emergency room right away. 

There is a way to proactively find out a pet’s allergic triggers and distinguish between food and environmental allergies. Veterinarians at Sploot can facilitate food trials to zero in on a dog’s or cat’s food allergies. Once allergies are pinpointed, veterinarians can recommend dietary optimizations and medications for managing allergies in dogs and cats.

3. Infections (Bacterial, Viral, or Parasitic)

Certain bacterial and viral infections can cause diarrhea in cats and dogs. These are often accompanied by a fever and lethargy. Some of the most common bacterial and viral culprits that cause diarrhea in dogs and cats include the following. (Take note of how diarrhea in cats and dogs differs depending on the pathogen):

Parasitic infections can also lead to diarrhea in dogs and cats. The following parasites in dogs and cats are known to cause diarrhea, along with their distinguishing symptoms:

If a dog or cat is suffering from what appears to be bacterial, viral, or parasitic infections, it’s best to consult a veterinarian for proper evaluation and treatment. 

Note: Some of the pathogens listed above (i.e. Parvovirus, Feline Panleukopenia, and Canine/Feline Coronavirus) are pet urgent care cases because of a high risk of fatality if prompt treatment is not given. 

4. Stress and Anxiety

Stressful situations, such as moving to a new home, changes in routine, or being separated from an owner (separation anxiety), can lead to stress-related diarrhea in dogs and cats. In many cases, stress- or anxiety-related diarrhea in cats and dogs is acute and short-term

Nevertheless, managing stress is crucial for a pet’s well-being. It is generally recommended to remove the cause of a pet’s stress (if possible) or to make use of techniques to help the dog or cat cope. For some dogs and cats, veterinarians may prescribe medication for managing anxiety — whether it is used for a one-off situation or more long-term. When in doubt, consult your veterinarian.

A cat hiding, showing signs of anxiety and stress, common causes of diarrhea in cats as well as diarrhea in dogs

5. Toxin Ingestion

Pets may ingest toxic substances, including certain human foods, plants, and chemicals, which can result in poisoning and diarrhea. Identifying and preventing access to these substances is vital. 

To minimize the chances of toxin ingestion, we encourage pet parents to learn more about what types of food are safe — and which ones aren’t. Refer to our guides to get a better idea of safe and unsafe foods/substances for dogs and cats: 

Safe vs Toxic Foods For Your Dog

Top 10 Healthiest Human Foods Dogs Can Eat

Top 10 Healthiest Human Foods Cats Can Eat

Human Indulgences - Yay or Nay for Cats & Dogs

6. Inflammatory Bowel Disease (IBD)

Another common cause of diarrhea in cats and dogs is Inflammatory Bowel Disease (IBD). Inflammatory Bowel Disease is a chronic condition characterized by inflammation in the digestive tract. Bacterial and viral infections, as well as a pet’s genetics, are predisposing factors to Inflammatory Bowel Disease.

When a dog or cat is suffering from Inflammatory Bowel Disease, they may exhibit watery diarrhea as well as mucus and blood on their stool. Though there is no cure for Inflammatory Bowel Disease, prompt veterinary attention leads to early diagnosis; the veterinarian will also be able to recommend any necessary dietary modifications and medications to help control the condition. 

7. Recent Antibiotic Usage

Diarrhea in dogs and cats is a possible side effect of antibiotic usage. Antibiotics can disrupt the balance of gut bacteria, causing antibiotic-induced diarrhea. This type of diarrhea can happen weeks after antibiotic usage. Typically, antibiotic-induced diarrhea in dogs and cats is seen in excessive amounts, and, at times, the stool may contain blood. 

It's crucial to follow your veterinarian's guidance when administering medications. If symptoms arise even with proper drug dosing, reach out to an urgent pet care veterinarian promptly. In some cases, veterinarians may prescribe probiotics, to help balance out the dog’s or cat’s gut flora — along with supportive care. 

8. Pancreatitis

Another possible cause of diarrhea in cats and dogs is acute or chronic pancreatitis. Pancreatitis in dogs and cats, which involves the inflammation of the pancreas, can lead to digestive problems — including diarrhea.

Excess weight and a high-fat diet are predisposing factors for pancreatitis in cats and dogs; ingestion of high fat treats like bacon, butter, cheese, and other greasy foods can often lead to acute pancreatitis.

Aside from diarrhea, other symptoms of pancreatitis in dogs and cats include vomiting, weakness, having a hunched position, and fever. In many cases, pancreatitis requires immediate veterinary attention. Make sure to contact a veterinarian if you observe these symptoms.

A dog looming over fatty food, which is linked to acute pancreatitis, one of the common causes of diarrhea in dogs and diarrhea in cats

Final Thoughts About Diarrhea in Dogs & Cats

Understanding the causes of diarrhea in dogs and cats is the first step in ensuring your pets' well-being. If your pet experiences persistent or severe diarrhea, reach out to a veterinarian to identify the underlying cause and receive appropriate treatment. Diarrhea can be a symptom of various health issues, and early diagnosis and intervention are crucial for your furry friends' health. Our team is always here to help!

Sploot Veterinary Care is a primary & urgent pet care veterinarian with convenient clinic locations and daily appointment availability, 365 days a year. If you’d like to have your pet checked for diarrhea in dogs or cats, our vet clinic doors are open for extended hours.

Book an appointment online, through the Sploot Vets app, or come on in for a walk-in appointment! As always, we’re with you every pounce of the way!