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By Judyvein Cheng, CPCN, BRNC
Certified pet nutritionist in Singapore
QUICK ANSWER
The best probiotic is the right type, at the right dose, for your dog's situation. Look for a label that lists each strain and its CFU count, includes a prebiotic, and has no fillers. Soil-based probiotics are the hardiest, lactic acid strains help with diarrhoea, and S. boulardii protects the gut during antibiotics. And rotate between brands.
Gut bacteria play a huge part in both health and disease, so giving the right probiotic at the right time can make a real difference. For why your dog needs a dog-specific probiotic in the first place, read why your dog needs a dog-specific probiotic. This guide is the practical part: how to choose one.
A quick refresher: the microbiome
Bacteria live all along the digestive tract: few in the stomach, more through the intestines, and most in the colon. Together with other microbes, they make up the microbiome, which scientists call the "forgotten organ". Every dog's microbiome is unique, shaped by their environment and diet.
Probiotics are living organisms that benefit health. They're found in the gut, in fermented foods and in supplements, and some yeasts count as probiotics too. They:
✓ Support gut health and digestion
✓ Produce vitamins K and B
✓ Produce serotonin and influence mood
✓ Lower gut pH and crowd out harmful bacteria
✓ Produce enzymes and fatty acids that discourage harmful bacteria
✓ Support the immune system
How probiotics support immunity
Gut bacteria ferment the fibre your dog can't digest, producing short-chain fatty acids (SCFAs): acetate, propionate and butyrate. SCFAs feed good bacteria and discourage harmful ones, help form the protective mucus layer, keep the gut lining tight (preventing leaky gut), help lower blood sugar, support T-cells to reduce chronic inflammation, help protect against food allergens, and improve the absorption of calcium, magnesium, iron and other nutrients. About 80% of the immune system lives in the gut, so a diverse, well-populated gut matters.
Probiotics have been linked to helping with leaky gut, yeast overgrowth, UTIs, diarrhoea, colitis and bowel disease, pancreatitis, obesity, allergy symptoms and mood. Things that disrupt the gut include antibiotics and other drugs, toxins, ageing, and high-starch or high-fat diets. The more diverse the gut, the better it copes with these shifts.
Don't forget the prebiotic
Probiotics need food. Prebiotics are soluble, indigestible fibres that feed them. Without prebiotics, probiotics are less active, less effective, and can die off, and many supplements don't include one. Look on the label for dandelion root, burdock root, larch arabinogalactan or inulin (from chicory).
Prebiotic foods include bananas, apples, cooked mushrooms, Jerusalem artichoke, chicory root and asparagus, plus garlic at the right dose. Choose organic, and gently cook and purée vegetables.
The three types of probiotic
Probiotics fall into three main groups, each with its own strengths.
1. Lactic acid probiotics
The most common type, often made from fermented milk. On labels you'll see abbreviations like L. acidophilus or B. longum. Lactobacillus turns milk sugar into lactic acid, which inhibits harmful bacteria. Bifidobacterium lives in the colon, works closely with immune cells, and low levels are linked to anxiety. These strains are fragile and usually stay in the gut for about 24 hours, though their benefits can continue. They're especially useful for diarrhoea.
L. acidophilus
Well researched in dogs. Increases Lactobacillus, reduces harmful clostridia and has good effects on immunity.
L. casei
Lives in the mucus lining and is part of the gut-brain axis, so it may affect mood.
L. plantarum and L. rhamnosus
Survive well, help build the colon wall in IBS and reduce antibiotic-related diarrhoea. Low L. rhamnosus is linked to anxiety.
B. animalis
Helpful for acute diarrhoea.
B. longum
Part of the gut-brain axis. A Purina study found higher numbers reduced signs of stress. May help diarrhoea and food allergies.
Enterococcus faecium
Survives stomach acid better than most lactic strains. There are concerns about antibiotic-resistant enterococcal infections in people, but it's considered beneficial for dogs.
Pediococcus acidilactici
Promising dog studies for skin conditions and leaky gut.
2. Probiotic yeast
Saccharomyces boulardii is used in people for acute and chronic diarrhoea, and a recent dog trial showed similar benefits. It also helps against Candida and may calm immune signalling in chronic inflammation. Because antibiotics don't kill it, it can be given during a course of antibiotics to protect the gut and reduce antibiotic-related diarrhoea.
3. Soil-based (spore-forming) probiotics
Bacillus species form protective spores that survive heat, stomach acid and most antibiotics. They're found naturally in soil and water, which is why they're called soil-based.
Bacillus coagulans
Produces lactic acid, crowds out unfriendly bacteria and is anti-inflammatory. May help inflammatory gut disease and diarrhoea. A 2016 rat study showed improvement in rheumatoid arthritis.
Bacillus indicus
Produces carotenoid antioxidants, B vitamins, vitamin K2 and quinols. Helpful for dogs with EPI or who need digestive enzyme support.
Bacillus subtilis
A natural resident of a healthy dog gut. Historically used for UTIs before antibiotics, it supports IgA (often low in dogs with autoimmune issues), strengthens the gut lining and produces vitamin K.
Dairy allergy? Lactobacillus and Bifidobacterium products are often dairy-based. S. boulardii and soil-based probiotics aren't, so they're good options for dogs with dairy allergies.
Which probiotic for which situation?
During antibiotics
A 2018 study found Lactobacillus given after antibiotics delayed and only partly restored the microbiome. Choose S. boulardii or soil-based strains (B. subtilis, B. coagulans), which can be given alongside antibiotics.
Diarrhoea
A high-CFU lactic acid probiotic should help within a few days, and studies suggest it can roughly halve recovery time. Continue for a few weeks. For chronic diarrhoea, use a multi-strain probiotic with gut-soothing herbs, such as Gut Soothe, long term until it resolves.
Allergies
Probiotics may reduce harmful bacteria and inflammation, and studies show fewer symptoms in itchy dogs. Soil-based: 1–5 billion CFU. Lactic acid: choose multiple strains and at least 30 billion CFU. Read more in how to reduce allergens in your home.
How to read the label
✓ Each strain is listed by name, along with a guaranteed CFU count. Avoid products that don't say.
✓ A prebiotic is included.
✓ No fillers, starches, sugars or unnecessary inactive ingredients. Probiotics come as powders, chews, liquids, pastes and bites, so check the ingredients whatever the form.
✓ Watch for maltodextrin. It's often listed as an inactive ingredient in probiotics and other supplements, but maltodextrin is a type of sugar, whether it comes from an organic source or not.
✓ Multiple strains for broader support.
✓ Enough CFU: generally 6–10 billion or more for lactic acid products.
How much to give
Lactic acid strains: at least 10 billion CFU a day for healthy dogs, and 25–50 billion CFU for medium to large dogs with digestive or immune problems. Use multi-strain products.
S. boulardii: about 0.5–5 billion CFU.
Soil-based: about 1 billion CFU.
Rotate your probiotics
I recommend rotating probiotics between brands, rather than sticking to one forever. Different products bring different strains, which helps build a more diverse gut.
FROM MY EXPERIENCE
BeanBean rotates daily between Adored Beast Soil & Sea, Four Leaf Rover Gut Guard and Green Juju Leaf. Read more about her routine in why your dog needs a dog-specific probiotic.
Food sources of probiotics
Green tripe
The raw, unprocessed stomach lining of grazing animals, with living L. acidophilus and digestive enzymes.
Kefir
Fermented with kefir grains, from cow, goat, coconut or rice milk. Full of bacteria and yeasts, plus vitamins and protein. Try raw goat milk.
Probiotic yoghurt
Made with S. thermophilus and L. bulgaricus. But dairy can be inflammatory, most yoghurt has few probiotics, and most is high in sugar.
Fermented vegetables
Sauerkraut, kimchi and kombucha are easy to make at home. They're rich in prebiotics but can also feed harmful bacteria and yeast, so use them carefully and in moderation for dogs with SIBO or yeast.
When probiotics may not suit: SIBO
Small intestinal bacterial overgrowth (SIBO) means too many bacteria in the small intestine, which can impair digestion and absorption. It can be caused by high-sugar or high-carb diets, slow gut movement, and drugs such as antibiotics and steroids. Around 80% of people with chronic digestive issues are estimated to have SIBO, and dogs may be similar.
Signs include chronic or on-and-off diarrhoea, weight loss, reflux, gas, IBS or IBD, food intolerances, skin issues and leaky gut. If your dog gets worse on probiotics, SIBO may be the reason. In that case, soil-based probiotics are the better choice.
How long to give probiotics
✓ Every day, for prevention: fine for most dogs, especially dogs on processed or high-starch diets. Soil-based probiotics are best for daily use, as they're less likely to worsen SIBO. Dogs with excess gas or SIBO shouldn't take lactic probiotics daily.
✓ Diarrhoea: expect improvement within days, then continue for a few weeks.
✓ Chronic digestive issues: long term, until resolved.
Frequently asked questions
Are there side effects?
Probiotics are generally safe. Bloating, gas and tummy upset are the most common. The main risk is that a probiotic simply doesn't work for your dog.
Which type is best?
Soil-based probiotics are an excellent choice because they're the hardiest. But the best plan is to rotate.
Can I use a human probiotic?
You can, if it has no fillers, but a dog-specific probiotic is better. See why your dog needs a dog-specific probiotic.
What about cats?
See probiotics for cats.
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This article is for educational purposes and isn't a substitute for veterinary care. If you're concerned about your pet's health, please seek professional advice.
ABOUT THE AUTHOR
Judyvein Cheng, CPCN, BRNC
Judyvein is a Certified Professional Canine Nutritionist and Certified Raw Nutrition Coach for Cats & Dogs, and the founder of JOOF Holistic Pet. Her journey began with her Frenchie, Wangcai, and today she helps pet parents in Singapore take a root-cause approach to their pets' health.
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