Probiotics and prebiotics can be a great addition to your dog’s daily routine; they help to maintain gut health and they have relatively few known side effects (1). But, if you’re like most pet owners, then you’re probably not entirely sure how they work. Here's everything you should know about prebiotics and probiotics for dogs.

Officially, the FAO and WHO define probiotics as “live microorganisms, which confer health effects to the host if administrated in sufficient amounts” (2). Many studies have shown how probiotics improve metabolism, the immune system and intestinal barrier function (3, 4, 5, 6). What's even more interesting is that probiotics were shown to suppress age-related factors in the body and promote longevity (7).

Note: Interestingly, a canine microbiome is extremely similar to that of humans in its functionality and structure; therefore, conclusions of many human trial studies can be used and are predictive of results in dogs (8). We will use them in this article, too.

Your Dog’s Digestive System

A large portion of your dog’s immune system is the lymphoid tissue that’s located in a dog's digestive tract (9). This tissue serves as the first line of defense if a pathogen invades the dog's body and it also influences a dog's nutrition intake, metabolic and physiological functions of the dog's body, and energy expenditure (10).

Therefore, it’s important to a dog's immune system that the digestive tract is healthy and always ready to put up a good fight against invaders. And part of keeping a dog's digestive system healthy is keeping a balance between good and bad bacteria (11).

Bacteria: The Good, The Bad and The Ugly

Your dog’s gut contains both “good” and “bad” bacteria – they're part of natural gut flora, and there must be a balance between these for your dog to remain healthy (12, 13).

A dog’s digestive tract is exposed to a lot of “bad” bacteria, but fortunately, there is a host of beneficial bacteria in the gut to keep that “bad” bacteria in check. They do this by producing fatty acids that prevent harmful bacteria from taking over (14, 15).

If the good bacteria weren’t present, or if it were outnumbered, the intestines would be damaged by the flourishing “bad” bacteria and the dog's body would be unable to efficiently absorb nutrients (16).

Consequently, this then causes symptoms like weight loss, lethargy, diarrhea, dehydration, and increased noise in a dog's digestive tract (17, 18). Digestive tract damage also means allowing the intestines to absorb bad bacteria, putting the immune system at risk.

How Does Bacteria Get Out of Balance?

A lot of things can cause the balance of bacteria in your dog’s system to get thrown off, but one of the most common causes is antibiotic use (19).

Antibiotics are designed to kill off any kind of bacteria, and they often kill off the “good” bacteria as well as the “bad” one. This disrupts the microbiome of the gut by creating an imbalance of the natural bacteria that should aid in digestion. This is why many times your dog may have diarrhea when taking antibiotics.

Other causes of bacteria imbalance in dogs include:

  • Old age
  • Parasites
  • Autoimmune conditions
  • Times of extreme stress
  • Medications that influence the gut flora (like dewormer and steroids)
  • A diet that increases inflammation (for example, a diet that includes ingredients that your dog is allergic to or has a strong sensitivity to)


Prebiotics are comprised of fiber that cannot be digested. Since they cannot be digested, these prebiotics are carried to the dog's colon where they help to fuel a healthy environment by feeding the “good” bacteria that reside there (20, 21, 22).

Think of prebiotics like fertilizer that you would spread on your garden to help it grow. Prebiotics do the same for the good bacteria already present in your dog’s digestive tract so that they can keep “bad” bacteria in check.


Where prebiotics fuel good bacteria that are already present in your dog’s system, probiotics repopulate the “good” bacteria that are missing from your dog’s system (23). They do this by modulating the production of cytokines (TNF-α and IL-6) and then improving the immunity (24) and forming a protective layer through secretion of SIgA (25, 26).

For example, if your dog takes antibiotics and the good bacteria are destroyed by those antibiotics, this good bacteria will need to be replaced. So if prebiotics is the fertilizer for the good bacteria in your dog’s gut, think of probiotics as reseeding your garden after it has been destroyed in a storm.

Benefits of Using Probiotics/Prebiotics

A 2019 study demonstrated complete safety of administering probiotics to dogs.

For the best result, it's best to use a combination of both probtiocs and prebiotics. Digestive supplements like probiotics and prebiotics offer many of the already mentioned benefits above, as well as those mentioned below as proven in studies (27, 28, 29, 30, 31, 32, 33, 34):

  • Replenishing lost intestinal flora in dogs that have recently been on antibiotics.
  • Improving appetite and helping struggling dogs gain weight.
  • Decreasing inflammation in senior dogs and promoting longevity by reducing cell damage associated with aging.
  • Easing symptoms of and treating digestive diseases like irritable bowel syndrome (IBS) by reducing inflammation of the intestines.
  • Reduce the permeability of the intestines and controlling the inflammation caused by allergic reactions.
  • Significantly strengthen the immune system of the host.

Marcella D. Ridgway, VMD, MS, DACVIM also believes that probiotics may be beneficial for some other conditions according to her publication in a peer-reviewed journal:

“Giving your dog healthy bacteria may positively impact chronic GI abnormalities, obesity, liver disease, and mood and behavior disorders. A daily probiotic supplement may also provide some ancillary benefits for dogs such as better skin and coat appearance, a reduction in gas, improved breath, a reduction of allergy symptoms, a reduction in yeast-associated disorders, and help in regulating bowel function.”

Are There Any Side Effects to Prebiotics/Probiotics?

Prebiotics and probiotics are very unlikely to cause any negative side effects in a healthy dog.

That said, as with all things, older dogs, dogs with underlying health conditions, and very young dogs are more susceptible to complications and side effects so they should always be monitored closely by a vet while undergoing treatment.

Can Dogs Take Human Prebiotic/Probiotic Supplements?

Even though there have been no studies that indicate that human prebiotic and probiotic use in dogs is harmful, you should always turn to digestive supplements that have been formulated specifically with dogs in mind.

While the microbiome of dogs and humans is very similar, there are still a few differences between the human and canine digestive systems. For example, the digestive enzymes and the pH of your dog’s system are not the same as yours. These and other differences are considered when digestive supplements are made.

Choosing a Prebiotic/Probiotic Supplement for Your Dog

For the best results and achieving the above mentioned benefits, probiotic and prebiotic supplements are recommended over dog foods that claim to contain probiotic/prebiotic in their ingredients. This is because most of these foods do not have a significant enough amount to provide any effect (35).

“A few studies have shown that most commercial veterinary probiotics do not contain what they claim to contain—both the species that are present and the numbers of viable organisms…specific manufacturing standards and appropriate dosage levels have not been established [for canine probiotics]” – Scott Weese, DVM at the Department of Pathobiology at the Ontario Veterinary College.

The quote above emphasizes the lack of standards that govern various dog supplements. Always research the manufacturer of any supplement you are considering to be sure that they are a reputable company with stringent quality control and safety protocols in place.

You should also be sure that your dog's probiotic contains both Bifidobacterium and Lactobacillus bacteria. Veterinarians suggest using supplements that contain the following bacterium because there is scientific evidence supporting their efficacy (36, 37, 38, 39):

  • Enterococcus faecium
  • Lactobacillus acidophilus
  • Lactobacillus casei
  • Lactobacillus plantarum
  • Bifidobacterium bifidum
  • Bifidobacterium animalis

What to Keep In Mind When Buying Probiotics for Dogs

Since probiotics contain live bacterium and yeast, unlike prebiotics, there are a few things that you should consider when purchasing them.


Always store your probiotics according to the directions on the package – some of them may need to be stored in a refrigerator. All probiotics must be stored in a dry area away from direct sources of heat and moisture.

This doesn’t just apply to when you get those probiotics home. Leaving your dog's probiotics in the car while you run a few more errands can easily kill off the live bacteria and render the probiotics ineffective.

Date of Expiration

You also need to pay attention to the date of expiration on a probiotic before you purchase and (if it’s been stored in your cupboard for a while) before you give it to your dog.

Many manufacturers include a number on their packaging that tells you how many live bacteria will remain in the probiotic at the end of the product's shelf life. This can help determine just how much living bacteria is in a probiotic at any point during its shelf life.

In general, the closer a probiotic is to its shelf life expiration date, the fewer bacteria are still going to be alive in that product.

Recommended Probiotics and Prebiotics for Dogs

A Note of Caution

Always consult with your veterinarian before adding any supplement to your dog’s diet, including prebiotics and probiotics. Your dog's current health condition, age, diet and other factors will need to be considered.

I do not recommend trusting the internet or other dog owners who don’t know your individual dog. Your personal vet will be able to tell you which supplements – if any – are safe for your dog, as well as monitor your dog’s health while they are on them.

READ NEXT: 10 Reasons to Give Your Dog Probiotics (Based on Science)

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Diane has a PhD in Biology and has been teaching different angles of science for over 20 years. She's also a writer of all things scientific with a lot of passion for animal sciences and psychology, trying to make these topics easily understandable and accessible for everybody.