Common Side Effects of Probiotics in Dogs

  • By Raquel Astacio
Dog on hardwood floor looking sad

Probiotics are live bacteria presented in capsule or liquid form that provide numerous benefits to a dog’s overall health. Bacteria species found in most canine probiotics include Lactobacillus, Bifidobacterium and S. thermophilus, all gram-positive bacteria that colonize within a dog’s gastrointestinal system, eliminate harmful bacteria and restore optimal levels of “good” gut microbiota.

Probiotics are typically given to dogs suffering GI tract illnesses, chronic diarrhea or diarrhea associated with antibiotic use. However, probiotics are like “super” vitamins that improve all aspects of a dog’s health, ranging from enhancing immune system functioning to supporting intestinal absorption of nutrients necessary for keeping all dogs fit, happy and disease-free.

Do Probiotics Cause Side Effects in Dogs?

Any substance that contains ingredients capable of effecting changes with a living organism is going to produce side effects of varying degrees. Some of these side effects won’t manifest themselves enough to be physically experienced because they occur at the cellular level. Other side effects may extend beyond the cellular level in reaction to the dog’s body chemistry, which may be abnormal due to illness, hormonal irregularities or a compromised immune system.

Probiotic supplements are complete safe to give to dogs since they contain nothing but natural ingredients, i.e., probiotic bacteria that already exist in the canine GI tract. If side effects do occur after giving probiotics to a dog, they are usually associated with digestive issues, such as excess gas, constipation or diarrhea (if you are not already treating the dog for diarrhea). In addition, the dog’s health problems may worsen a bit before completely clearing up as the GI tract adjusts to the sudden influx of “good” probiotic bacteria.

Side Effects Resulting from Weakened Immune Systems in Dogs

Research into lactobacillus included in probiotic supplements has found that L. bacillus may thrive too much in a dog’s immune system weakened by disease, malnutrition or even old age. Although a rare occurrence, overgrowth of lactobacillus may allow bacteria to spill over into the dog’s bloodstream and produce a systemic infection or inflammation.

A senior dog laying on the front porch of a house

The immune system of a dog is weakened with old age.

Allergic Reactions to Probiotics

Experts estimate that only one in a million dogs and people could have an allergic reaction to probiotics for reasons that have yet to be identified. Signs that a dog may be suffering an allergic reaction to one or more of the live bacteria composing probiotic supplements are intense “all over” itching, difficulty breathing, swelling of the tongue and lips and unsteady gait. Dogs exhibiting these symptoms after being given probiotics should be taken to a veterinarian as soon as possible for supportive care.

Low Quality Probiotics May Cause Side Effects

Probiotics manufactured by inferior companies do not care about your dog’s healthy. They are only in the business to make a profit and produce cheap, unstable probiotics that quickly degrade in the dog’s stomach before reaching the intestines. Unless probiotic bacteria reach the dog’s intestines in tact and still retaining all their beneficial properties, they are essentially useless and may even be harmful to the dog once “seeded” in the GI tract.

Another problem with low quality probiotics is that they may labeled “for dogs” but are, in fact, meant for humans. Nearly all bacteria are host-specific, meaning that some bacteria are designed to exist in dogs and some specific to humans. Giving dogs human probiotic supplements may cause side effects that include vomiting, severe diarrhea and dehydration.

Canine-specific bacteria are:

Every one of these bacteria can be found in high-quality probiotics formulated especially for dogs. In addition, superior canine probiotics will offer the correct CFU, or “colony forming units“, beneficial to your dog’s health. A probiotic formula’s CFU is the total amount of bacterium in the formula. Some formulas combine all bacteria strains into one CFU count while others will list each strain of bacteria on the label, along with its unique CFU.

Cream colored pills of Lactobacillus acidophilus

Lactobacillus acidophilus is one of the beneficial bacteria in canines.

How Many Probiotic CFUs Do Dogs Need?

This depends on the type and severity of the dog’s health condition. Owners who put their dogs on canine probiotics should closely monitor the dog, observe their eating and sleeping habits, determine whether the dog’s energy level has increased and decide (with helpful input from a veterinarian) if the dose should be adjusted.

Depending on how much your dog weighs, a total CFU of one to four billion is extremely effective in restoring your dog’s health. To minimize the risk of side effects, dogs under 50 pounds should be given between one and three billion CFUs of probiotics for the first few days. Dogs weighing more than 50 pounds can handle between two and five billion CFUs per day. It’s also a good idea to divide dosages into two parts to be given at mealtimes.

Advantages of Probiotics for Dogs Clearly Outweigh the Minimal Risks

In addition to antibiotics causing GI tract disorders, chronic diarrhea, flatulence and appetite loss, other factors such as poor diet, stress, environmental changes and non-antibiotic prescription drugs can also deplete beneficial bacteria in the dog’s intestines. Probiotics not only promote growth of “good” bacteria in your dog’s intestines but will also:

  • Improve digestive processes by facilitating breakdown of consumed food, absorption of vitamins and minerals and removal of toxic waste products
  • May help reduce minor food intolerances and their side effects
  • Reduces inflammation in the GI tract to relieve diarrhea or constipation
  • Increases energy levels by eliminating some chronic health conditions
  • Promotes manufacturing of folic acid, biotin and B vitamins
  • Stimulates and regulates all components of the canine immune system
  • Helps degrade and neutralize food toxins and carcinogens
  • Keeps hormone levels balanced and regulated
  • May reduce the risk of female dogs suffering urinary tract infections
A dog jumping into water

Eliminating chronic health conditions through probiotics help increase energy levels in dogs.

Love Your Best Friend with Probiotics

Side effects of probiotics in dogs is minimal to none and should never deter a dog owner from giving their dog the great health benefits of safe, high-quality probiotics.

A dog tilting its head outside of a barn

Probiotics helps ensure your dog stays healthy, happy and most of all, energetic!

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Disclaimer: the advice and information in this article is not intended to be used as a replacement for professional medical advice from a veterinarian.



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  • I ran out of chihuahua’s probiotics about a week ago. I was wondering can stopping her probiotics can she get constipated ? My girl is constipated tonight, let out a yelp when she tried to go. I gave her pure pumpkin she didn’t like it so I heating up 1/2 cup of milk. At this point I don’t know how to help her. She never had this problem in years. She drinks quite a bit of water. I was wondering if the constipation is from her being without her probiotics. I can only buy them from Amazon my vet charges $2.00 a pill. Ordered them tonight but takes a few days. Any suggestions to help her I would appreciate

    Shelley Staffig 2 years ago Reply

  • My 11 year old chihuahua has had digestion problems for years. Vet prescribed Privable. Wow what a difference. I can’t affird to keep her on this brand. I bought the generic micro floral probiotic. It’s seems to have listed everything she needs. Only one bad thing I can only give her 1/2 a capsule so I am measuring out half of the capsule. Bought some gelliton capsules so re capsulimg them up for her. I worry I could give her to much. Well if this stuff makes her sick she is going back on the Proviable

    Shelley 2 years ago Reply

    • ProViable is available on Chewy dot com for what I would call a reasonable price. You can often get the syringes in farm supply stores such as TSC or Orscheln.

      Linda 2 years ago Reply

  • I purchased Herbsmith Microfloral. I was told to give my chihuahua 1/2 the capsule. I purchased some gelatin capsules and divided the capsules. I mix the powder with her food she’s had it twice. Today she woke up with stomach ache. I can hear the gas in her stomach. She was taking Proviable for 80 days. No problems worked great. I read These two are similar but are they? I am very worried is she getting sick from this new probiotic? The only reason I switched her from Proviable was the cost. Did I make a mistake? My chi weighs only 6lbs. Is this Microfloral too strong for her even though I divided the capsules. Anyone who reads my post I would really appreciate your opinion or advice. My baby is 11 she has had digestion problems most of her life. She has to eat Perscription dog food to. The food agrees with her, no problem with her food. No human food once in awhile a dream bone. That’s chicken and veggies.
    Thank you

    Shelley S 2 years ago Reply

  • My 12 year old Boxer was prescribed a 5 day supply of Probiotics to help with diarrhea and a very rummbling stomach. I gave the round pill once a day (3 at a time). After about 40 minutes of administering the dose she would start shaking and become very hyper and panting a lot. I went 3 days and stopped giving them to her. She is also acting very strange, She will go outside and stare at the door and not want to come in. I have to go outside and coax her in the door. (It’s 17 degrees where I live) Totally not normal for her. Is this a reaction to the Probiotic?

    Nancy B 2 years ago Reply

  • My dog will not eat. does this pill have any thing to do with this.

    Elsie A Sheets 2 years ago Reply

  • Ask recommendation from a vet before giving probiotics to your best buddy

    Anne C. Hornyak 1 year ago Reply

  • My 13 year old Shih Tzu will not eat after taking the paste. Is anyone having the same problem?

    Alyssa Anderson 1 year ago Reply

  • My pug took Proviable DC for dogs and within 3 days had horrible diarrhea. It had to be an underlying condition. That’s all we can think because probiotics normally don’t have any bad side effects. Trying another brand to be on the safe side

    Frank Iebr 1 year ago Reply

  • Reply to Alyssa Anderson . Our Dog is also a 13 YR old Shih Tzu . I give her about 4 ground up teaspoons of Royal Canin Gastrointestinal kibbles (the small ones) and 2 teaspoonful’s of Royal Canin Gastrointestinal canned dog food .. both from the vet , and I sprinkle I packet of FortiFlora on the above Royal Canin . The canned dog food she loves and she will not eat the mixture without it , but this is the stuff that gives her diarrhea , so I try to keep it to a minimum . Without the FortiFlora she gets diarrhea really bad , but she races to get this mixture once a day . and no diarrhea !

    Dave Ankenman 12 months ago Reply

  • I was instructed by my vet to give 1 cc every 8 hours but I accidentally gave my puppy 1 cc every hour. He is not acting weird and his diarrhea stopped. Can this action be harmful to my puppy?

    Paco 9 months ago Reply

  • My 16 lb poodle is on Fortiflora once a day. it works well, but he get diarrhea every once in a while. Can I give him pro pectalin also when this happens.

    Barbara lord 4 weeks ago Reply

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