Best Cat Immune Support Supplements (2026) – Top 10 Reviewed
A strong immune system is your cat’s first line of defense against infections, allergies, and illness. Whether you’re caring for a kitten still building immunity, an adult cat prone to seasonal sniffles, or a senior feline needing extra support, the right supplement can help keep your cat’s immune defenses in top shape. In this guide, we’ve researched and reviewed the best cat immune support supplements available so you can make an informed choice for your furry companion.
Our Top Picks at a Glance
- Best Overall: Pet Honesty Cat Immune Support Lysine – L-lysine with colostrum and quercetin
- Best Value: VetriScience Lysine Immunity Health Chews – Trusted vet brand at an accessible price
- Best Premium: Dr. Bill’s Feline Immune Support – Colostrum, beta glucan, and turkey tail mushroom
Quick Comparison
| Product | Key Ingredients | Form | Servings | Best For |
|---|---|---|---|---|
| Pet Honesty Cat Immune Support Lysine | L-Lysine, Colostrum, Quercetin, Omega-3 | Crunchy Chews | 30-day supply | Overall immune & allergy support |
| VetriScience Lysine Immunity Chews | L-Lysine 250mg, Immune Blend | Soft Chews | 120 | Budget-friendly lysine support |
| Dr. Bill’s Feline Immune Support | Colostrum, Beta Glucan, Turkey Tail, Zinc, Vitamin C | Powder | 60 | Premium multi-pathway immune support |
| Vetoquinol Viralys L-Lysine Powder | L-Lysine 500mg | Powder | 200 | Respiratory and eye health |
| Felisyl L-Lysine Soft Chews | L-Lysine, Immune Support Blend | Soft Chews | 60 | Easy-to-give lysine treats |
| In Clover Spry Respiratory Support Chews | L-Lysine, Superfoods, Prebiotics | Soft Chews | 60 | Respiratory and ocular health |
| Tomlyn Immune Support L-Lysine Chews | L-Lysine, Fish Flavor | Chews | 30 | Short-term immune boost |
| Pet Wellbeing Life Gold for Cats | Burdock Root, Sheep Sorrel, Cat’s Claw | Liquid | Varies | Holistic detox and immune defense |
| Nutramax Imuquin Cat Immune Health | Beta-Glucan, Astaxanthin | Sprinkle Capsules | 30 | Science-backed beta-glucan support |
1. Pet Honesty Cat Immune Support Lysine – Best Overall
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A comprehensive immune and allergy relief chew that goes well beyond basic lysine supplementation.
Pet Honesty’s immune support formula combines L-lysine—the go-to amino acid for feline immune health—with colostrum, quercetin, and omega-3 fatty acids. L-lysine is widely recommended by veterinarians for cats prone to upper respiratory issues and herpes virus flare-ups. Colostrum provides natural antibodies and immunoglobulins, while quercetin acts as a natural antihistamine that can help soothe sneezing, runny noses, and itchy skin.
These crunchy and creamy chicken-flavored chews are designed as a 30-day supply and have quickly become one of Amazon’s best-selling cat supplements. The dual-texture format is a hit with cats, and the clean ingredient list—free from fillers, artificial preservatives, and colors—gives pet parents confidence in what they’re feeding.
What We Like
- Multi-ingredient formula addresses immune support, allergy relief, and respiratory health
- Colostrum and quercetin add meaningful benefits beyond basic lysine
- Crunchy-and-creamy texture that 9 out of 10 cats reportedly enjoy
What Could Be Better
- 30-day supply means frequent reordering for long-term use
- Only available in chicken flavor
Bottom Line: Pet Honesty delivers the most well-rounded cat immune supplement on the market, combining lysine with colostrum, quercetin, and omega-3s in a treat cats love.
2. VetriScience Lysine Immunity Health Chews – Best Value
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A trusted veterinary brand offering 120 lysine immune chews at an accessible price point.
VetriScience is one of the most recognized names in veterinary supplements, and their Lysine Immunity Health Chews deliver 250mg of L-lysine per chew along with an immune support blend. These chicken-flavored soft chews are formulated specifically for cats and kittens dealing with allergies, sneezing, runny noses, and watery eyes.
With 120 chews per bag, this product offers outstanding value for daily supplementation. VetriScience’s reputation for veterinarian-formulated products backed by research gives this supplement extra credibility. The soft chew format is gentle on teeth and easy for most cats to eat.
What We Like
- 120-count bag provides excellent value for daily use over several months
- Backed by VetriScience’s veterinary reputation and research-based formulation
- Soft chew format is easy for cats of all ages to consume
What Could Be Better
- Lower lysine dose per chew (250mg) may require multiple chews daily for some cats
- Some cats may not find the flavor as appealing as competing products
Bottom Line: VetriScience’s lysine chews combine trusted quality with generous quantity, making them the best value for daily feline immune support.
3. Dr. Bill’s Feline Immune Support – Best Premium
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A veterinarian-designed powder that deploys colostrum, beta glucan, turkey tail mushroom, zinc, and vitamin C for comprehensive immune defense.
Dr. Bill’s takes feline immune support to the next level with a multi-pathway approach. Colostrum provides natural immunoglobulins and growth factors, beta glucan activates immune cells like macrophages and neutrophils, and turkey tail mushroom contributes polysaccharides that have been studied for their immune-modulating effects. The formula is rounded out with zinc and vitamin C for foundational immune support.
As a powder supplement, it’s designed to be mixed into your cat’s food daily. The formula is suitable for cats of all ages, making it a versatile option for multi-cat households with varying immune needs.
What We Like
- Turkey tail mushroom and beta glucan offer advanced immune-modulating support
- Veterinarian-designed formula with clinical reasoning behind each ingredient
- Suitable for cats of all ages, from kittens to seniors
What Could Be Better
- Premium pricing reflects the advanced ingredient list
- Powder format may not appeal to all cats, especially dry food feeders
Bottom Line: Dr. Bill’s is the go-to choice for cat owners who want the most advanced, science-informed immune support formula available.
4. Vetoquinol Viralys L-Lysine Powder – Best for Respiratory Health
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A pure L-lysine powder from a trusted veterinary pharmaceutical company, specifically designed for respiratory and eye health support.
Vetoquinol’s Viralys is one of the most widely recommended lysine supplements among veterinarians. It delivers a straightforward 500mg of L-lysine per serving in a fish-flavored powder that’s easy to sprinkle on food. L-lysine is particularly valued for supporting immune health in cats prone to feline herpesvirus, which can cause recurring upper respiratory infections, sneezing, and eye discharge.
The 100-gram container provides approximately 200 servings, making it one of the longest-lasting options on this list. The simplicity of a single-ingredient formula appeals to cat owners who want targeted lysine supplementation without unnecessary additives.
What We Like
- Trusted veterinary pharmaceutical brand with wide veterinarian recommendation
- 200 servings per container offers exceptional longevity
- Pure lysine formula without unnecessary fillers or additives
What Could Be Better
- Single-ingredient formula doesn’t provide broader immune support
- Fish flavor may not appeal to all cats
Bottom Line: Vetoquinol Viralys is the gold standard lysine supplement for cats with respiratory or herpesvirus-related immune concerns.
5. Felisyl L-Lysine Soft Chews – Best Treat-Style Lysine
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Salmon-flavored soft chews that make daily lysine supplementation feel like treat time for your cat.
Felisyl’s soft chews deliver L-lysine in a format that most cats find irresistible. The salmon flavor and soft texture make these chews easy to give as a daily treat, removing the struggle that can come with powder or tablet supplements. The formula supports immune health, respiratory function, and eye health—the three areas where lysine supplementation is most beneficial for cats.
Each container provides 60 soft chews, and the recommended dosage makes this a convenient one-to-two month supply depending on your cat’s needs. Made in the USA, Felisyl has built a reputation for quality lysine products in multiple formats.
What We Like
- Salmon flavor is a hit with most cats, making daily dosing easy
- Soft chew format is gentle and appealing compared to tablets or powders
- Made in the USA with a focus on quality ingredients
What Could Be Better
- Fewer chews per container compared to some competitors
- Higher per-serving cost than powder alternatives
Bottom Line: Felisyl is the best choice if your cat won’t eat powders and you want a treat-style lysine supplement they’ll look forward to daily.
6. In Clover Spry Respiratory & Immune Support Chews – Best with Prebiotics
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A unique formula that combines L-lysine with superfoods and prebiotics for immune support that starts in the gut.
In Clover’s Spry chews recognize the important connection between gut health and immune function. The formula pairs L-lysine for respiratory and ocular support with prebiotics to nourish beneficial gut bacteria, which play a crucial role in overall immune response. Superfood ingredients round out the blend, providing antioxidants and micronutrients that further support the immune system.
Each container holds 60 soft chews, and the dual approach of immune support plus digestive health makes this a standout for cats that could benefit from both. The chews are formulated specifically for cats and designed for daily use.
What We Like
- Prebiotic inclusion supports the gut-immune connection for more holistic support
- Superfood ingredients provide additional antioxidant and nutritional benefits
- Specifically formulated for feline respiratory and ocular immune needs
What Could Be Better
- Less widely available than some bigger-name competitors
- May take longer to see results compared to pure lysine products
Bottom Line: In Clover Spry is ideal for cat owners who want immune support that also nurtures digestive health through prebiotics.
7. Tomlyn Immune Support L-Lysine Chews – Best Starter Option
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A 30-count lysine chew that’s perfect for trying out immune supplementation without a large commitment.
Tomlyn’s fish-flavored lysine chews are a straightforward, no-frills option for cats needing immune support. The smaller 30-count package makes this an ideal starter product if you want to test whether your cat will accept lysine chews before investing in a larger supply. Tomlyn is a well-established pet health brand, and their formula focuses on delivering effective lysine supplementation in a palatable chew.
These chews are designed for daily use and support immune health, respiratory function, and eye health. The fish flavor is generally well-received by cats, making it a reliable first step into immune supplementation.
What We Like
- Smaller pack size is perfect for trying before committing to a larger supply
- Established pet health brand with a track record of quality products
- Fish-flavored chews appeal to cats’ natural taste preferences
What Could Be Better
- Only 30 chews means frequent reordering for ongoing supplementation
- Higher per-chew cost compared to buying larger quantities
Bottom Line: Tomlyn’s compact package is the perfect way to introduce your cat to lysine supplementation and see how they respond before buying in bulk.
8. Pet Wellbeing Life Gold for Cats – Best Holistic Formula
- BETTER QUALITY OF LIFE. Is your feline friend thriving? We’d be honored to help your cat live their happiest and healthiest life possible.
- IMMUNE SUPPORT. Vet-strength Immune Sure herbal formulation supports your cat's natural immune defenses and innate resistance to help keep them healthy and strong.
- ANTIOXIDANT-RICH. Antioxidants in Immune Sure, including vitamin C, help protect your cat from oxidative stress due to free-radical damage, which is essential for immune resilience.
- VITALITY. Supports your cat’s long-term health and vitality so they can enjoy a greater quality of life well into their golden years!
- VETERINARIAN-FORMULATED. MADE IN USA. MONEY-BACK GUARANTEE. TRUSTED CARE SINCE 2001. Expertly developed by our compassionate team of in-house holistic veterinarians to offer your pet essential health support, our vet-formulated supplements reflect over 20 years of leadership in pet wellness. Proudly produced in FDA-registered, GMP-certified facilities in the USA, each product is made with the highest-quality ingredients and undergoes rigorous testing for purity.
A liquid herbal formula that supports detoxification and immune defenses using traditional botanicals like burdock root and sheep sorrel.
Pet Wellbeing’s Life Gold takes a holistic approach to feline immune support with a liquid formula featuring burdock root, sheep sorrel, cat’s claw, and other traditional herbs. The formula is designed to support the body’s natural detoxification processes while strengthening immune defenses. It’s NASC-certified and veterinarian-formulated, which provides assurance of quality and safety.
The 2-ounce liquid bottle makes dosing flexible—you can add it to food, water, or administer it directly. This format is especially useful for cats that refuse solid supplements entirely.
What We Like
- NASC-certified and vet-formulated for trusted quality assurance
- Liquid format allows flexible and precise dosing
- Holistic botanical approach supports detox and immune defense simultaneously
What Could Be Better
- Herbal taste may not be appealing to all cats without mixing into food
- Smaller bottle may not last as long as chew or powder alternatives
Bottom Line: Pet Wellbeing Life Gold is the best choice for cat owners who prefer a traditional herbal approach to immune support and detoxification.
9. Nutramax Imuquin Cat Immune Health – Best Science-Backed Formula
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A veterinary-grade sprinkle capsule featuring beta-glucan and astaxanthin for targeted immune cell activation.
Nutramax’s Imuquin stands apart from lysine-based supplements by focusing on beta-1,3/1,6-glucan, a compound sourced from yeast cell walls that has been researched for its ability to activate key immune cells like macrophages and neutrophils. Astaxanthin, a powerful carotenoid antioxidant from green algae, provides additional immune and cellular protection. This two-ingredient approach is simple but backed by solid science.
The sprinkle capsule format makes administration easy—just open a capsule and sprinkle the contents directly onto your cat’s food. Each box contains a 30-day supply, and Nutramax’s reputation in veterinary supplements gives this product strong credibility.
What We Like
- Beta-glucan is one of the most researched immune-activating ingredients available
- Sprinkle capsule format is mess-free and easy to add to meals
- Nutramax is a highly respected name in veterinary nutritional supplements
What Could Be Better
- Does not include lysine, so it won’t address herpesvirus-specific concerns
- 30-day supply requires monthly reordering
Bottom Line: Imuquin is the best option for cat owners who want a research-backed, non-lysine immune supplement from a top-tier veterinary brand.
How to Choose the Best Cat Immune Support Supplement
The most important factor in choosing an immune supplement for your cat is identifying what specific immune concern you’re trying to address. If your cat suffers from recurring upper respiratory infections or has been diagnosed with feline herpesvirus, L-lysine supplements are widely recommended by veterinarians as a first-line immune support. Lysine helps suppress herpesvirus replication while supporting overall immune function.
For broader immune support that goes beyond respiratory health, look for supplements containing ingredients like colostrum, beta-glucan, or medicinal mushrooms such as turkey tail. These ingredients work through different immune pathways—colostrum provides natural antibodies, beta-glucan activates immune cells, and mushroom polysaccharides modulate the immune response. A multi-ingredient formula can provide more comprehensive protection.
The format of the supplement matters more than you might think. Cats are notoriously picky, and the best supplement in the world won’t help if your cat refuses to eat it. Soft chews and crunchy treats tend to have the highest acceptance rates, while powders work well for cats that eat wet food. Liquid supplements offer the most flexibility but may need to be mixed with food to mask the taste.
Consider your cat’s life stage and health status. Kittens and senior cats often benefit most from immune supplementation, as their immune systems are either still developing or naturally declining. Cats undergoing stress—from moves, new pets, or boarding—can also benefit from temporary immune support. Always check that the supplement is appropriate for your cat’s age and consult your vet if your cat is on medications.
Benefits of Cat Immune Support Supplements
A well-functioning immune system helps your cat fight off everyday pathogens, from common respiratory viruses to bacterial infections. By supplementing with immune-supportive ingredients, you can help strengthen your cat’s natural defenses, which may result in fewer sick days, less severe symptoms when illness does occur, and faster recovery times.
For cats with feline herpesvirus—which is estimated to affect a significant portion of the cat population—lysine supplementation can help manage flare-ups. The virus tends to reactivate during periods of stress, and consistent lysine supplementation may help keep symptoms like sneezing, nasal discharge, and eye irritation under control.
Immune supplements that include antioxidants like quercetin, astaxanthin, or vitamin C can also help manage allergic responses. These ingredients may reduce histamine release and inflammation, potentially easing symptoms like itchy skin, runny eyes, and sneezing caused by environmental or food allergies.
Frequently Asked Questions
What is L-lysine and why is it important for cats?
L-lysine is an essential amino acid that plays a key role in immune function, particularly in cats with feline herpesvirus (FHV-1). It’s believed to help suppress viral replication and support the immune system’s ability to fight off respiratory infections. Most veterinarians consider it a safe and beneficial daily supplement for cats prone to upper respiratory issues.
Can I give my cat immune supplements every day?
Most cat immune supplements are designed for daily use and are safe for long-term supplementation. However, you should always follow the dosing instructions on the product label and consult your veterinarian, especially if your cat has underlying health conditions or is taking medications.
Are immune supplements safe for kittens?
Many lysine-based supplements are safe for kittens, often at a reduced dosage. Always check the product label for age recommendations. Products like Vetoquinol Viralys specifically note their suitability for kittens, while other supplements may be intended for adult cats only.
How do I get my picky cat to take an immune supplement?
Start with a treat-style supplement like soft chews, which many cats will eat willingly. If that doesn’t work, powder supplements mixed thoroughly into wet food are often the next best option. Liquid supplements can be added to food or water as a last resort. Some owners have success warming wet food slightly to enhance the aroma and mask the supplement.
Can immune supplements replace veterinary care?
No. Immune supplements are meant to support your cat’s health alongside proper veterinary care, not replace it. If your cat is showing signs of illness—lethargy, loss of appetite, persistent sneezing, eye discharge, or fever—see your veterinarian promptly.
Do indoor cats need immune supplements?
Indoor cats can still benefit from immune supplements, especially if they’ve been exposed to feline herpesvirus, experience seasonal allergies, or live in multi-cat households where illness can spread easily. Stress from environmental changes can also weaken an indoor cat’s immune response, making supplementation beneficial during transitions.
What’s the difference between lysine supplements and broader immune formulas?
Lysine supplements focus specifically on supporting immune function against herpesvirus and respiratory infections. Broader immune formulas may include additional ingredients like beta-glucan, colostrum, mushroom extracts, or antioxidants that support the immune system through multiple pathways. The best choice depends on your cat’s specific needs.
