Critical Immune Defense

Protect your pet’s immune system and help prevent cancer with Critical Immune Defense, made from one of nature’s most effective cancer-fighting ingredients!

Coriolus Versicolor Mushroom Extract is clinically proven to boost immunity, fight cancer and alleviate medical treatment-related discomfort in dogs and cats.

Harvested in the woods of the Northeastern United States from wild-grown turkey tail mushrooms, Coriolus Versicolor Mushroom Extract is packed with antiviral molecules that provide a big boost to immune systems. Research has revealed they contain B-glucans, which when ingested by dogs and cats, activate receptors in the small intestine that quickly and effectively boost immunity. This process helps animals to resist stress factors, including the side effects of cancer therapy.

Coriolus Versicolor Mushroom Extract is a leading supplement administered by physicians to their human patients fighting cancer. Critical Immune Defense finally makes it available in doses safe for dogs and cats. Now your pets can get the same immunity-boosting benefits that have previously only been readily available for humans.

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Boosted Immunity:
Increases the ability of dogs and cats to fight off illnesses and diseases of all types, including cancers.

Cancer Fighting
The molecular ingredients found in Coriolus Versicolor Mushroom Extract enhance the body’s production of naturally occurring killer cells that attack cancer cells before they grow.  

Reduce Cancer Treatment Side Effects
Critical Immune Defense’s key ingredient prevents radiation therapy-induced immune suppression and can prevent immunity depletion caused by chemotherapy.

Improved Gut Health
Coriolus Versicolor Mushroom Extract is stuffed with compacted mycelium, an enzyme-loaded antimicrobial agent that helps offset digestive problems associated with our pets’ modern diets.

Preventative Care
Many pet cancers are not discovered until it’s too late...when an organ such as the spleen ruptures and the animal collapses. Critical Immune Defense provides an important safeguard against sudden illness.

No Side Effects
Subjects participating in clinical studies of the effectiveness of Coriolus versicolor mushroom in alleviating the ill effects of cancer treatment reported no adverse effects, but did report an improved immune response.

Maintain Healthy Appetite
Pets love the delicious, natural flavors found in CID, and because there is no nausea associated with Coriolus versicolor mushroom they will never shy away from eating their daily dose.

All Natural
Safe and natural formula that is made in the USA with no artificial ingredients, flavors or fillers.

Safe To Combine
Critical Immune Defense is safe to combine with other medicines and supplements, including VetSmart Formulas’ Hip & Joint Complex for dogs


Polysaccharopeptide, known more widely as PSP, is the bioactive agent extracted from Coriolus versicolor mushroom. PSP has been proven to inhibit the growth of tumors in animals, specifically having been shown to delay the progression of metastases and increase survival rates of animals with cancer. The same studies show that PSP has no damaging effects on healthy cells.

Known in China as Yunzhi and as turkey tail in North America, Coriolus versicolor mushrooms have been used in herbal medicine for more than 2,000 years. While not yet approved for treatment in humans in the United States, physicians in Japan and China have widely administered PSP to their human patients undergoing cancer chemotherapy and other treatments.

Researchers at the world-renown University of Pennsylvania School of Veterinary Medicine have conducted a randomized, double-blind, multidose study of PSP administered to dogs stricken with cancer. Among their findings:
-The development and advancement of abdominal metastases “was significantly delayed.”
-Median survival time for dogs given the highest doses of PSP was 43 percent higher than dogs given no PSP.
-The results were greater than researchers anticipated, sparking follow-up trials that are currently underway.

Additional investigative trials in China have recently shown that PSP:
-Boosts immune cell production,
-Alleviates chemotherapy symptoms, and
-Improves healthy T-cell production.

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Critical Immune Defense

Protect your pet’s immune system and help prevent cancer with Critical Immune Defense, made from one of nature’s most effective cancer-fighting ingredients!

120 tablets are included in every bottle.

The Natural Solution Veterinarians Trust

The Natural Solution Veterinarians Trust

VetSmart Formulas was originally designed for veterinarians. This means they deliver the clinical-strength quality and efficacy veterinarians demand in products they prescribe and recommend. They are wheat-free and contain no artificial colors or flavors. Even more, they’re safe for dogs with allergies and can be used along with most prescription medications. In fact, many prescription medications have harmful side-effects and you can use VetSmart Formulas to replace medications such as Rimadyl, Deramaxx, Metacam, and Previcox and get the same great results!

Manufactured In The USA To The Highest Quality Standards!

Manufactured In The USA To The Highest Quality Standards!

We use the best manufacturers in the industry! Our products are made in FDA audited facilities which operate using current good manufacturing practices (cGMP). Additionally, our manufacturers are audited by Underwriter Labs. All the ingredients are inspected and tested before processing. This ensures we deliver consistently safe, high-quality products to you!


Here’s what people are saying about VetSmart’s Critical Immune Defense:


The 100% No-Risk Promise

Order right now with confidence!
The cost of VetSmart starts at less than the price of a cup of coffee per day!
Try it out for 30 days and if it doesn’t work for your dog, you’ll get your money back!
There’s absolutely no-risk in giving it a try.

MSRP $129.95

Sale: $99.95


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*The statements on this website have not been evaluated by the Food and Drug Administration. The information on this website is not intended to replace medical advice from your pet health care professional. These products are not intended to treat, cure, or prevent any disease. If your pet has a medical condition, is taking medication, is pregnant or nursing we recommend that you consult your pet health care professional before using these products.

Return Policy

VetSmart Formulas strives to keep your dog moving pain-free, which is why we offer a 30-day, money-back guarantee. If at any point you decide it’s not the best dog supplement on the planet, remember you are protected by the highest standard 100% money-back guarantee. Just send us the empty bottles and we’ll refund you to the last penny, no questions asked. If after 30 days of use, you are unhappy and would like a refund, here’s exactly what to do:

-Contact the VetSmart Formulas team by calling 888-212-8400 Monday through Friday between the hours of 9:00am and 4:00pm Pacific Standard Time. We will gladly provide you with our return address, and a return confirmation number. This is an easy and effortless process.

-Return the empty canister, your original invoice, and the confirmation number you have been assigned.

-It is your obligation to pay the return postage, and we do recommend you opt for tracking and confirmation numbers for verification and efficiency purposes. Note: We must receive the canister within 45 days from the date of original purchase for the refund to be valid.

- We will refund your entire order as long as all bottles purchased are returned.

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These guidelines were created to keep you satisfied, while at the same time ensuring we can continue to provide a quality product to other happy customers for years to come. Returning VetSmart Formulas without complying with our policy will unfortunately deem your transaction non-refundable.

After complying with the steps above, please allow adequate time for shipping, quality control, and communication with credit card companies and banks as you patiently await your refund.