FIGHT VIRUSES, DISEASES, AND CANCERS.

Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats
Critical Immune Defense for Dogs & Cats

Critical Immune Defense for Dogs & Cats

Sale price$65.00 USD
Size: Small Bottle | 70 Scoops
Free shipping on all US mainland orders

There simply isn't another product of this quality and strength available on the market, with THOUSANDS of testimonials about the results!

Critical Immune Defense is a safe, all-natural immune booster that can add years to the life of your dog or cat.
Made in the USA with certified organic mushrooms.

Just sprinkle a small amount of powder on your dog or cat's food. It tastes great, even for the most finicky of pets!

✔︎ Boosts immune system

✔︎ Reduces inflammation

✔︎ Promotes normal cell growth

✔︎ Protects against toxins in food, water & environment

✔︎ Supports long-term health in dogs and cats
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"I've lost two golden retrievers to cancer, so I've been doing a ton of research since I got my newest puppy. I want to give him the best chance of living a long and healthy life and Critical Immune Defense is a key part to that equation. He likes it and I believe in being proactive! So glad I found this company!"

- Audrey (Verified Customer)

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⭐️⭐️⭐️⭐️⭐️

“My cat is 15 and has feline herpes. In the past, I have given her lysine with very little results. Since taking Critical Immune Defense I have seen a steady improvement. Hardly any eye discharge and her nose isn’t wet anymore. No difficulty breathing at all. My son said, “What took you so long to find this stuff?” I also give it to my 3-year-old dog, she’s healthy but …..just in case. They both eat it and have no problem eating all their food.”

- Lisa (Verified Customer)

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Featured on
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"Wish there was a human version!! Our large male German shepherd was getting growths on his neck and by his eye. They were getting larger. I saw this product and ordered one canister, not expecting much. However, within 2 weeks, the growths were getting smaller. They finally disappeared! We now give this as a preventative to both of our dogs! Highly recommend it!! Worth the money!!"

- Carla (Verified Customer)

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"30 days ago I went to a cancer specialist who told me that my dog’s prognosis was not very good and he would eventually get lumps and tumors all over his body. I left very depressed.
I found your product online by a miracle, and I started giving it to him. I don't know what it’s doing, but all older cancer tumors are gone and it seems to have eliminated the new tumors as well. I've been giving the VetSmart product twice a day for approximately 30 days. I'm just so grateful and so thankful that it works so well. He is looking really, really good. Thank you so much! I need to order more soon.”

- Paul (Verified Customer)

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Your pet's immune system is the key to its health! Here's why:

It’s your job to feed and nourish it, and make sure it operates at optimal levels to fight disease and cancers. In today’s world, viruses and diseases are rampant, and it can be challenging to protect your pet.

Let’s face it: your pet lives in a world filled with contamination.

They spend 90% of their waking hours on the floor, mopping up toxins, chemicals, and pollutants.

The household cleaning products, fertilizer on the lawn, and preservatives in their foods can be harmful. Bacteria, airborne contaminants, and viruses transmitted by humans can challenge their health.

Most pets do not eat an optimal diet, and likely do not get as much exercise as they require.

What do you do?

You need to put your pet’s immune system in overdrive! Research shows that a well-balanced and functional immune system is essential to your pet’s overall health and well-being.

"The immune system acts like a nonstop housekeeper", describes Dr. Donna Raditic, an American College of Veterinary Nutrition (ACVN) diplomate in Athens, Georgia.

It identifies potentially harmful pathogens like bacteria, viruses, fungi, and parasites, then works to eliminate them before they can do harm.

And a pet's immune system monitors cells to ensure they’re working properly.

“When other cells are aging or functioning abnormally—such as a cancer cell reproducing too rapidly—the immune system attempts to step in and maintain proper physiological function and balance,” Dr. Raditic explains.

Your pet's immune system is the key to its health! Here's why:

It’s your job to feed and nourish it, and make sure it operates at optimal levels to fight disease and cancers. In today’s world, viruses and diseases are rampant, and it can be challenging to protect your pet.

Let’s face it: your pet lives in a world filled with contamination.

They spend 90% of their waking hours on the floor, mopping up toxins, chemicals, and pollutants.

The household cleaning products, fertilizer on the lawn, and preservatives in their foods can be harmful. Bacteria, airborne contaminants, and viruses transmitted by humans can challenge their health.

Most pets do not eat an optimal diet, and likely do not get as much exercise as they require.

What do you do?

You need to put your pet’s immune system in overdrive! Research shows that a well-balanced and functional immune system is essential to your pet’s overall health and well-being.

"The immune system acts like a nonstop housekeeper", describes Dr. Donna Raditic, an American College of Veterinary Nutrition (ACVN) diplomate in Athens, Georgia.

It identifies potentially harmful pathogens like bacteria, viruses, fungi, and parasites, then works to eliminate them before they can do harm.

And a pet's immune system monitors cells to ensure they’re working properly.

“When other cells are aging or functioning abnormally—such as a cancer cell reproducing too rapidly—the immune system attempts to step in and maintain proper physiological function and balance,” Dr. Raditic explains.

⭐️⭐️⭐️⭐️⭐️

“I have a rescue and keep 8 senior and special needs cats. I give them this for cats, and it has proven to extend the lives of those who were in danger of losing their lives from cancer, renal failure, and, frankly, only God knows what else! I am grateful for this formula being available for seniors we adore and aren’t really ready to cross the 🌈 yet❣️👍😻 This was Foxy Loxy. He had been failing(14 yrs old), but as he received Pet Wellness Support, he recovered his enjoyment of life, and I could love him for 2 more years❣️ I have other kitties' who had experienced similar recoveries through Pet Wellness. Thank you again!”

- Mat (Verified Customer)

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⭐️⭐️⭐️⭐️⭐️

"My female pitbull was diagnosed with lymphoma back in 2020. We did chemo for 2 years. During this time, I found the product and started using it on all my dogs, even healthy ones.

We are now in almost 4 years later, and my girl Haven has been in remission for almost 2 years. I only give the product in the dinner feedings. I believe it saved her."

- Diane (Verified Customer)

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52%

CANCER RATES ARE SKYROCKETING

THE DOCTORS AGREE

Mushrooms = Anticancer Activity

“As a pet lover, I think it makes sense that the compounds in mushrooms be included in your pet’s diet or included by nutritional supplements. Certain mushrooms contain agents with anticancer activity and immunomodulatory properties that may help fight cancer and certain other diseases.”

- Dr. Frank Markland, Professor of biochemistry and molecular medicine at the University of Southern California Keck School of Medicine.

Pet owners CAN make a difference.

“It is the responsibility of the pet owner to do everything possible to minimize the risk of cancer in their pets. This includes a sensible lifestyle with sufficient exercise, weight management, drinking clean water, healthy food intake, and avoiding toxins. Giving your pets a high-quality antioxidant supplement is highly recommended to further reduce the risk of cancer.”

– Dr. Shawn Messonnier, Veterinarian and Founder of Paws & Claws Animal Hospital in Plano, Texas.

More dogs and cats are being diagnosed with cancer than ever before. 

“Certain mushrooms and turmeric may be beneficial in helping your pet to boost its immune system to fight diseases,” explains Edwards.

“Cancer is affecting our pets at alarming rates, and it is devastating for both the families of these pets as well as the pets themselves. I am seeing this in my practice on a regular basis.”

- Dr. Jennifer Edwards, Veterinarian at Ponemah Veterinary Hospital in Amherst, New Hampshire.

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"Sienna is 13 years old and is on two of your products. She been on this for several weeks and noticing a difference in enjoying the stairs again. Thank you for both! ❤️❤️❤️
Critical Immune Defense, has made a huge difference with a lump on her shoulder! Sienna is taking two of your products Critical Immune Defense, for a lump on her shoulder which has shrunk, to half its size after finishing first container, working on
Papilloma virus warts and skin tags...have two containers to go.
Sienna started having issues using the steps. I started her on your Hip+Joint product and within 10 days, no longer any issues. Sienna will be 14 this year. Loving these products 🙏🏻🤞🏻 in time Critical Immune Defense will help with the virus...."

- Gloria (Verified Customer)

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Organic Turkey Tail Mushrooms

This colorful mushroom has been used for centuries in Asia to treat disease and contains high levels of active compounds that have been proven to inhibit the growth of cancerous tumors.

✔︎ Delivers significant amounts of tumor-fighting Polysaccharopeptides (PSPs)

✔︎ Approved by the United States Food & Drug Administration for use in treating prostate and breast cancer in humans

✔︎ Proven to delay the growth of cancerous tumors in pets and improve their survival rate

Organic Reishi Mushrooms

This woody fungi is known as one of the top natural superfoods and has been used for 1000s of years to fight inflammation, cancer, heart disease, hormonal imbalances and more.

✔︎ Contains beta-glucans that increase the immune system’s T-cell levels

✔︎ Lowers inflammatory responses caused by stress, poor diet, and other environmental factors

✔︎ Contains ganoderic acids that have been shown to lower cholesterol levels and blood pressure

Organic Shiitake Mushrooms

According to the Journal of Nutrition, shiitake mushrooms provide antiviral, antibacterial and antifungal protection and help to control blood sugar and reduce inflammation.

✔︎ Contains all 8 essential amino acids as well as linoleic acid, an essential fatty acid

✔︎ Used in Japan to treat heart disease, hepatitis, high blood pressure, and infectious diseases

Organic Maitake Mushrooms

Maitake mushrooms are loaded with vitamins and active ingredients that stimulate the immune system and promote natural hormone balance and healthy cell growth.

✔︎ Contains beta-1, 6 glucan polysaccharide components that stimulate the immune system and reduce abnormal cell growth

✔︎ Used in Asia to help minimize the toxic effects of radiation and chemotherapy treatment

White Turmeric Root Extract

Turmeric has been used for centuries to reduce pain and inflammation. Its active ingredient, curcumin, has proven to be effective at blocking the growth of certain cancers and protecting against neurodegenerative diseases, arthritis, cardiovascular risks and liver damage.

Our proprietary extract is six times more bioavailable than standard turmeric root, which means it’s more effectively absorbed into your pet’s body and they need less of it to get the same effect. It’s also colorless and milder tasting, making it easier to handle -- and tastier for your pet! No more turmeric stains!

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⭐️⭐️⭐️⭐️⭐️

"My dog is now 21 years old and this has helped so much. She is on her 3rd bottle, things were grown on face they are much smaller. She used to go to bathroom on herself, now she gets out of bed to go. She is close to 22, she eats at least 2 big meals a day! I know each day is a blessing with her! She is a Boston terrier and Rat terrier. this has helped tremendously! Thank you for giving her new time! Her eyes have also gotten much brighter too!"

- Gina (Verified Customer)

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Not only is it easy to use (just sprinkle it over your pet’s food), but also your pet will love the taste!

It’s your job to feed and nourish it, and make sure it operates at optimal levels to fight disease and cancers.
Order now

Not only is it easy to use (just sprinkle it over your pet’s food), but also your pet will love the taste!

It’s your job to feed and nourish it, and make sure it operates at optimal levels to fight disease and cancers.
Order now

Not only is it easy to use (just sprinkle it over your pet’s food), but also your pet will love the taste!

70 Scoops in a small bottle
210 scoops in a large bottle
10% Additional Saving

⭐️⭐️⭐️⭐️⭐️

"This product has been a blessing for our Ellie. Diagnosed with mast cell cancer given 1 year to live that was almost 4 yrs ago. She will be 12 in a few months we started her on this when she was 8 yr old. Still doing fantastic plays and acts like a puppy. Love this product.”

- Edie (Verified Customer)

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The All-Natural Solution. Trusted By Veterinarians.

Originally designed for veterinarians, VetSmart Formulas delivers the clinical-strength, quality and efficacy veterinarians demand of solutions they provide and recommend.

Critical Immune Defense is 100% safe to use, has NO side effects, and can be used in conjunction with chemotherapy, steroid treatments and other medications.

✔︎ Certified organic mushrooms

✔︎ No artificial colors or flavors

✔︎ Wheat-free

NEW Enhanced Formula

Discover Our Enhanced Formula!

We've improved our formula! The new product may appear lighter in color and have a slightly different texture (but the same great taste), thanks to our innovative use of the fruiting body and mycelium of the four mushrooms, instead of mushroom extracts.

 Why the Change?

Traditional mushroom extracts are processed using heated water, which is then sprayed to create a powder. Our research suggests that this heat processing can diminish the valuable nutrients in the mushrooms.

Understanding Fruiting Body and Mycelium

Fruiting Body: This is the part of the mushroom you're familiar with—the cap and stem.

Mycelium: These are the nutrient-packed roots and base of the mushroom.

We use the entire mushroom, grinding it into a nutrient-dense powder that boasts higher levels of beta-glucans and polysaccharides than extract powders. Independent testing has shown that our new mushrooms contain up to 250% more beta-glucans and polysaccharides.

Research-Backed Benefits

According to research published by the National Library of Medicine, beta-glucans and polysaccharides are renowned for their metabolic and immunomodulatory properties, including anticancer, antibacterial, and antiviral effects. In some countries, the mushrooms we use in Critical Immune Defense are prescribed not only to prevent cancers and diseases but also to effectively treat them.

Organic and Sustainable

Our mushroom blend is organically grown in Canada on sustainable farms using patented and breakthrough growing processes to enhance the full spectrum of bioactive compounds. It doesn't get any better for your pet!

Experience the powerful benefits of our enhanced formula and give your pets the best in health and wellness!

Made in the USA to the highest quality standards.

VetSmart Formulas is made in the USA in FDA audited facilities which adhere to cGMP and are audited by Underwriter Labs. Every ingredient is carefully inspected and tested before processing, ensuring a consistently safe, high-quality product for your beloved pet’s health.

Frequently Asked Questions

Still have questions?

Talk to us on Facebook Messenger

Or give us a call at 888-212-8400 Mon-Fri 9:00 to 5:00 PST

Returns | 30-Day Money Back | Ingredients

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average rating 4.8 out of 5
Based on 1608 reviews
  • 5 Stars
    1366 Reviews
  • 4 Stars
    171 Reviews
  • 3 Stars
    61 Reviews
  • 2 Stars
    2 Reviews
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    8 Reviews
96% of reviewers would recommend this product to a friend
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1608 Reviews
Reviewed by Vanessa a. A.
Verified Buyer
Review posted
I recommend this product
Rated 5 out of 5
Pet Age
10+ Years
Dog Breed
Alaskan Malamute
Pet Problem(s)
  • Tumor
Will Consume Product
Enjoyed
Pet Happiness
Just Right

Critical immune defense

Hi, I found a lump on my boy Henley when I was giving him a bath. Offcourse I started framing out. I am opting to not do anything because I cannot afford the cost of veterinary care and also because my boy just turned 11. I want to enjoy him with quality of life. I came across your product, I have been giving it to him for a bout a month it’s too soon to say it’s a miracle but I am very hopeful. Thank you

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Pet Wellness Direct

Thank you for sharing Henley’s story with us. 💛 We understand how concerning it can be to discover a lump on your beloved boy. We’re glad Critical Immune Defense has given you some hope as you focus on his comfort and quality of life. 🐶✨ We encourage having any new lump evaluated by a veterinarian when possible and wish you and Henley many more happy moments together.

Reviewed by Stephanie L.
Verified Buyer
Review posted
I recommend this product
Rated 5 out of 5
Pet Age
7 - 10 Years
Pet Problem(s)
  • Tumor
  • Inflammation
  • Joint Pain
Will Consume Product
Devoured
Pet Happiness
Tail Wagging

Helped senior Great Dane

Our 9 yr old Dane started having redfish yellow mucus discharge about a year ago. We got an endoscopy and they didn’t see any growths or tumors in his sinuses/throat. The vet told us he likely has a tumor further up in his cranium that he couldn’t see, and that he was towards the end of the life span for a Dane so we were going to have to ride it out. I’ve tried a bunch of different supplements over the last year to help. We were wiping his nose constantly and washing our couch cushions weekly. He’s now been on this for 2 months and he’s been mucus free for a month. I was completely shocked. 10/10!

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Pet Wellness Direct

Thank you for sharing your Great Dane’s experience! 💛 We’re so glad to hear you’ve noticed such an encouraging improvement after a challenging year. 🐶✨ We truly appreciate your trust in Critical Immune Defense and wish your sweet boy continued comfort and many more happy days ahead!

Reviewed by Deborah B.
Verified Buyer
Review posted
I recommend this product
Rated 5 out of 5
Pet Age
10+ Years
Cat Breed
Bengal
Pet Problem(s)
  • Cancer
  • Tumor
  • Bad Breath
Will Consume Product
Nibbled
Pet Happiness
Just Right

High Quality Immune Support

I've been giving this to my cat for 18 months now to help boost her immune system since being diagnosed with a bleeding liver tumor. I had a second ultrasound done last month to see what the status of the tumor was as the vets all said it's an aggressive tumor and she might have days or weeks. The latest ultrasound showed very little growth on 2 margins and a reduction in size by a small amount from the other margin. I didn't expect the tumor to be stopped in its tracks. Now she does have some episodes where it bleeds and causes her pain but that's not often. I ran out of the product a couple months ago and she went without it for 5 days until it arrived and she did end up having a pain episode. So yes, this mushroom blend and nutritional supplement, IS VERY CRITICAL to have for my girl. It has been her best defense against a tumor that has responded very well to these potent immune modulators. Very pleased with this product! I put it in capsules since she won't eat it on her own. This supplement is 100% worth every penny!

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Pet Wellness Direct

Thank you for sharing your sweet girl’s remarkable journey. 💛 We’re so glad to hear she has enjoyed more precious time with you and that her recent ultrasound brought encouraging news. 😺✨ We truly appreciate your 18 months of trust in Critical Immune Defense as part of her care routine and wish her continued comfort and many more cherished moments together.

Reviewed by Cynthia W.
Verified Buyer
Review posted
I recommend this product
Rated 5 out of 5
Pet Age
10+ Years
Dog Breed
Golden Retriever
Pet Problem(s)
  • Low Energy
  • Joint Pain
Will Consume Product
Enjoyed
Pet Happiness
Tail Wagging

10 months on Critical Immune Defense!

Molly started on CID December 12,2025 She was 10.5 years old Had a couple of noticeable masses in her lower abdomen She was sluggish & was having difficulty moving her bowels Her energy level had dropped significantly Within a month she had made great strides towards improvement! Energy increased, appetite returned stool movement improved She was swimming in the pool again & playing with her son Very happy with the results & will continue using it as long as we have Golden Retrievers

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Pet Wellness Direct

Thank you for sharing Molly’s wonderful progress! 💛 We’re so happy to hear your sweet Golden Retriever has regained her energy, appetite, and enthusiasm for swimming and playing with her son. 🐶✨ It’s especially encouraging to hear about her improved digestion and quality of life. We truly appreciate your continued trust in Critical Immune Defense and wish Molly many more happy, active days ahead!

Reviewed by Elizabeth A.
Verified Buyer
Review posted
I recommend this product
Rated 5 out of 5
Pet Age
7 - 10 Years
Dog Breed
Shih Tzu
Pet Problem(s)
  • Tumor
Will Consume Product
Nibbled
Pet Happiness
Just Right

This works

I tried critical immune defense before in the past and it’s not cheap so I didn’t want to do the recommended dosage for my two Shih Tzu’s, and they are both very healthy and they were fine and there was really nothing I was addressing. Years later, my male had a lump in his armpit so I ended up getting the bigger size giving them the recommended dosage each day and it has now been one month and I can’t even feel the lump anymore. Definitely definitely worth the money and definitely worth buying. It would’ve been thousands of dollars to have him undergo another surgery, this is a much better alternative. Also, they usually fight some sort of allergy this time of year, the scratching in the looking as not been an issue this year at all. This is definitely a great product, and definitely worth the money.

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Pet Wellness Direct

Thank you for sharing your Shih Tzus’ experience! 💛 We’re so glad to hear you’ve noticed encouraging changes in your boy’s lump and that both dogs are doing well during allergy season. 🐶✨ We truly appreciate your trust in Critical Immune Defense and are happy it has become a valued part of their wellness routine!

Research and references Peer-reviewed studies on the ingredients, with links to PubMed

Critical Immune Defense combines four medicinal mushrooms (Turkey Tail, Reishi, Shiitake and Maitake) with milk thistle, a bioavailability-enhanced turmeric extract and antioxidant nutrients. Below is the independent, peer-reviewed research on those ingredients, with the species each study was carried out in. It is the same research we send to veterinarians who ask.

Turkey Tail mushroom (polysaccharopeptide, PSP)

Turkey Tail is the most studied medicinal mushroom in dogs. Researchers at the University of Pennsylvania tested a Turkey Tail polysaccharopeptide in dogs with splenic hemangiosarcoma and reported a dose-related delay in the spread of the disease. A larger follow-up study in 101 dogs did not find a survival benefit when the same compound was added to chemotherapy. We cite both, because that is the honest state of the evidence: Turkey Tail is an immune-modulating ingredient with real canine research behind it, not a cancer treatment. In people, a Cochrane review and a meta-analysis of 23 trials found Turkey Tail and Reishi products used alongside standard cancer care were linked to modest survival and immune-cell benefits.

Research:

  • Brown & Reetz (2012). Single agent polysaccharopeptide delays metastases and improves survival in naturally occurring hemangiosarcoma. Evid Based Complement Alternat Med. Study population: Dogs (15; splenic hemangiosarcoma). PubMed
  • Gedney (2022). Evaluation of the anti-tumour activity of Coriolus versicolor polysaccharopeptide (I'm-Yunity) alone or in combination with doxorubicin for canine splenic hemangiosarcoma. Vet Comp Oncol. Study population: Dogs (101; splenic hemangiosarcoma). PubMed
  • Pilkington (2022). Coriolus (Trametes) versicolor mushroom to reduce adverse effects from chemotherapy or radiotherapy in people with colorectal cancer. Cochrane Database Syst Rev. Study population: Humans (colorectal cancer RCTs). PubMed
  • Zhong (2019). Coriolus Versicolor and Ganoderma Lucidum Related Natural Products as an Adjunct Therapy for Cancers: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Front Pharmacol. Study population: Humans (23 RCTs, 4,246 patients). PubMed

Reishi, Shiitake and Maitake mushrooms

Mushroom beta-glucans are the compounds behind most of the immune research. In a 2024 trial, 32 healthy dogs fed fungal beta-glucans showed higher neutrophil phagocytic activity, a measure of first-line immune response. A dose-response study in 40 beagles found Reishi increased phagocytic activity at the higher dose tested. Shiitake powder raised antioxidant enzyme activity in healthy dogs, and a shiitake-derived extract (AHCC) reduced parasite load over two years in a randomized, placebo-controlled trial in dogs with leishmaniosis. A 2026 feeding trial found a Turkey Tail and Reishi blend was well tolerated in cats and shifted gut metabolites, though immune markers were mostly unchanged.

Research:

  • de Souza Theodoro (2024). Beta-glucans from Euglena gracilis or Saccharomyces cerevisiae effects on immunity and inflammatory parameters in dogs. PLoS One. Study population: Dogs (32 healthy). PubMed
  • Kayser (2024). Functional properties of Ganoderma lucidum supplementation in canine nutrition. J Anim Sci. Study population: Dogs (40 adult beagles). PubMed
  • Kusaba (2024). Shiitake mushroom powder supplementation increase antioxidative activity in dogs. Front Vet Sci. Study population: Dogs (healthy). PubMed
  • Miró (2024). New immunomodulatory treatment protocol for canine leishmaniosis reduces parasitemia and proteinuria. PLoS Negl Trop Dis. Study population: Dogs (client-owned, leishmaniosis). PubMed
  • Wang (2026). Effects of a mushroom-based beta-glucan and bovine colostrum blend on the gastrointestinal health and immune function of healthy adult dogs. J Anim Sci. Study population: Dogs (20 healthy beagles). PubMed
  • Broughton (2026). Effects of a mushroom-based beta-glucan blend on the gastrointestinal health and immune function of healthy adult cats. J Anim Sci. Study population: Cats (20 healthy adults). PubMed
  • Fries-Craft (2023). Dietary yeast beta 1,3/1,6 glucan supplemented to adult Labrador Retrievers alters peripheral blood immune cell responses to vaccination challenge without affecting protective immunity. J Anim Sci. Study population: Dogs (24 adult Labradors). PubMed

Milk thistle (silymarin and silybin)

Milk thistle is included for liver and antioxidant support, which matters most for pets on long-term medication or chemotherapy. In a randomized trial in dogs with cancer, silybin (with SAMe) reduced the rise in liver enzymes caused by the chemotherapy drug lomustine. Silybin lowered liver enzymes in healthy dogs and in dogs with liver disorders, and the ACVIM consensus statement on canine chronic hepatitis describes silymarin's antioxidant, anti-inflammatory and anti-fibrotic actions. A 2023 review covers its use in both dogs and cats.

Research:

  • Skorupski (2011). Prospective randomized clinical trial assessing the efficacy of Denamarin for prevention of CCNU-induced hepatopathy in tumor-bearing dogs. J Vet Intern Med. Study population: Dogs with lymphoma, mast cell tumor or histiocytic sarcoma on CCNU. PubMed
  • Gogulski (2021). Effects of silybin supplementation on nutrient digestibility, hematological parameters, liver function indices, and liver-specific mi-RNA concentration in dogs. BMC Vet Res. Study population: Dogs. PubMed
  • Giannetto (2022). Antioxidant and Hepatoprotective Effect of a Nutritional Supplement with Silymarin Phytosome, Choline Chloride, l-Cystine, Artichoke, and Vitamin E in Dogs. Antioxidants (Basel). Study population: Dogs. PubMed
  • Webster (2019). ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs. J Vet Intern Med. Study population: Dogs (consensus). PMC
  • Tedesco & Guerrini (2023). Use of Milk Thistle in Farm and Companion Animals: A Review. Planta Med. Study population: Dogs and cats (review). PubMed

Turmeric extract (curcumin)

Curcumin has a large laboratory literature on antioxidant and inflammatory-response pathways; what matters for pets is absorption, which is why this formula uses a bioavailability-enhanced white turmeric extract. In cats, a 2026 randomized trial found curcumin added to standard care improved kidney and antioxidant markers in cats with chronic kidney disease, and a four-month tolerance study found a turmeric extract safe in healthy cats. In dogs, curcuminoids reduced a marker of oxidative stress in diabetic dogs, and a 2026 trial found a turmeric extract eased osteoarthritis signs. A University of California, Davis pilot study showed curcumin can be given safely to dogs with cancer but did not shrink tumors, which is why we do not make that claim.

Research:

  • Ilgun (2026). Renoprotective effects of curcumin in cats with chronic kidney disease. J Vet Intern Med. Study population: Cats (16 client-owned, IRIS stage 3 CKD). PubMed
  • Raynaud (2026). A Tolerance Study of Turmeric Extract in Healthy Adult Cats. Animals (Basel). Study population: Cats (healthy adults). PubMed
  • Suemanotham (2022). Curcuminoid supplementation in canine diabetic mellitus and its complications using proteomic analysis. Front Vet Sci. Study population: Dogs (6 diabetic, 12 healthy). PubMed
  • Tripathi (2026). Protective effects of turmerosaccharides rich extract of Curcuma longa L. in osteoarthritic dogs. Front Vet Sci. Study population: Dogs (20 with osteoarthritis). PubMed
  • Withers (2018). In vitro and in vivo activity of liposome-encapsulated curcumin for naturally occurring canine cancers. Vet Comp Oncol. Study population: Dogs (10; cancer). PubMed
  • Moritz (2026). In vitro effects of apigenin, curcumin, and fumaric acid on intracellular ROS and TNF-alpha responses in Escherichia coli-stimulated canine PBMCs. Front Vet Sci. Study population: Canine blood mononuclear cells. PubMed

Vitamin E, selenium, vitamin C, CoQ10 and vitamin A

These nutrients support the antioxidant system that mushrooms and curcumin act on. Vitamin E and selenium together enhanced lymphocyte and phagocyte activity in adult cats. Organic selenium raised antioxidant enzymes and lymphocyte proliferation in puppies, and a systematic review summarises selenium's role in canine immunity. Diets with added vitamin E, vitamin C and beta-carotene improved antioxidant status in both dogs and cats, and beta-carotene (the vitamin A precursor) restored age-related declines in T-cell response in older dogs. CoQ10 supplementation changed inflammatory and lymphocyte measures in a controlled study in dogs.

Research:

  • O'Brien (2015). Moderate dietary supplementation with vitamin E enhances lymphocyte functionality in the adult cat. Res Vet Sci. Study population: Cats (adult). PubMed
  • Shao (2021). Supplemental Dietary Selenohomolanthionine Improve Antioxidant Activity and Immune Function in Weaned Beagle Puppies. Front Vet Sci. Study population: Dogs (30 weaned beagle puppies). PubMed
  • Zentrichova (2021). Selenium and Dogs: A Systematic Review. Animals. Study population: Dogs (systematic review). PubMed
  • Jewell (2024). Effect of dietary antioxidants on free radical damage in dogs and cats. J Anim Sci. Study population: Dogs (40) and cats (40). PubMed
  • Massimino (2003). Effects of age and dietary beta-carotene on immunological variables in dogs. J Vet Intern Med. Study population: Dogs (36 young and old). PubMed
  • Hall (2011). Influence of dietary antioxidants and fatty acids on neutrophil mediated bacterial killing and gene expression in healthy Beagles. Vet Immunol Immunopathol. Study population: Dogs (50 adult beagles). PubMed
  • Druzhaeva (2022). Effects of Coenzyme Q10 Supplementation on Oxidative Stress Markers Inflammatory Markers Lymphocyte Subpopulations and Clinical Status in Dogs with Myxomatous Mitral Valve Disease. Antioxidants. Study population: Dogs (MMVD). PubMed

For veterinarians

The full veterinary research overview for Critical Immune Defense, including label amounts per scoop, weight-based dosing and an evidence hierarchy for each ingredient, is available on request. Two points deserve emphasis in professional discussion. First, the Turkey Tail evidence is mixed: the 2012 pilot (n=15) was encouraging and the 2022 prospective study (n=101) found no survival benefit from adding PSP to doxorubicin, with a sex-dependent effect. Second, curcumin bioavailability varies widely between preparations, so results from liposomal or dietary curcumin cannot be assumed to transfer. The finished product has not been evaluated in a controlled trial. Wholesale for clinics is available through Vetcove.

About this research

Critical Immune Defense is a nutritional supplement, not a drug. The studies above were conducted by independent researchers on individual ingredients, not on the finished VetSmart Formulas product, and are provided so that pet owners and veterinarians can read the evidence for themselves. Results in one species or preparation do not guarantee the same result in another. This information is not intended to diagnose, treat, cure or prevent any disease. If your pet has a diagnosed condition or takes medication, talk to your veterinarian before adding a supplement.