7 Anti-Inflammatory Effects of Quercetin Noted by Veterinarians — Feeding Guide for Dogs

ImmunityIngredientsMeongsiljang Veterinary Advisory Board

Quercetin is a natural flavonoid found abundantly in onions, apples, and berries, and it is used to help alleviate allergic itching and chronic inflammation in dogs and cats. Here’s a summary of weight-based dosages, administration on an empty stomach, and breeds to watch out for.

What Is Quercetin?

An image showing onions, apples, and berries, which are rich in quercetin.

Quercetin is a natural flavonoid antioxidant found abundantly in plants such as onions, apples, berries, and broccoli. Its potential use for alleviating allergies and itching in dogs and cats is currently under research. The most critical factor is dosage. The weight-appropriate dose, whether it should be administered on an empty stomach, and any breed-specific precautions must always be determined in consultation with a veterinarian. Although sometimes referred to as a "natural antihistamine," this is not an established veterinary term. Unlike conventional medications, quercetin does not produce immediate effects; its efficacy should be evaluated through consistent administration and ongoing monitoring of the pet's response.

Key Effects of Quercetin

Quercetin is gaining attention for pets because research suggests it may help suppress inflammation, allergies, and oxidative stress.

Antihistamine effect: While it may inhibit histamine-related responses, its efficacy in veterinary clinical practice has not yet been fully established.

Anti-inflammatory effect: Research is exploring its potential to inhibit inflammation-related enzymes, but direct clinical evidence for its use in pet skin and joint inflammation remains limited.

Antioxidant effect: It has properties that neutralize free radicals, and studies are investigating its potential to prevent cellular damage caused by oxidative stress.

Immune modulation: It may help regulate hypersensitivity reactions, but its role in managing atopic and food allergies should be evaluated under veterinary guidance.

Respiratory support: Research is examining its potential effects on bronchial inflammation, but consulting a veterinarian before clinical application is essential.

How Far Does the Veterinary Evidence Go?

In veterinary pharmacology textbooks and clinical dermatology, quercetin is approached as an adjunctive agent. This means it does not completely replace steroids or immunomodulators, and research is ongoing into its potential for concurrent use. In practice, vitamin E is recognized for its immunomodulatory and anti-inflammatory effects through lysosomal stabilization, reduced prostaglandin E2 synthesis, and increased interleukin (IL)-2 production. It has been reported to be used as an adjunctive therapy alongside immunosuppressants in immune-mediated skin diseases such as cutaneous lupus erythematosus, sterile panniculitis, and dermatomyositis. However, in the case of atopic dermatitis, while placebo-controlled studies have reported a reduction in lesion scores, it is important to remember that no significant effect on pruritus (itching) itself was confirmed. Although combining quercetin with such nutrients is conceptually proposed, large-scale randomized controlled trials specifically on quercetin remain limited. For safety, always consult your veterinarian to approach quercetin as an adjunctive therapy rather than a standalone treatment.

An image of a veterinarian examining a puppy's skin.

Ingredients Frequently Used with Quercetin

Safe

케르세틴(Quercetin)

항히스타민·항염·항산화

Dosage: 체중 1kg당 8mg (1일 1~2회)

수의피부과학 보조 요법 권장

Safe

브로멜라인(Bromelain)

케르세틴 흡수율 증가, 소염

Dosage: 케르세틴 용량의 1/2

흡수 보조제로 병용

Safe

오메가3(EPA/DHA)

피부 장벽·항염 시너지

Dosage: 체중 1kg당 EPA+DHA 50~75mg

아토피 관리 1차 보조

Caution

비타민E

항산화 시너지

Dosage: 소형견 25~50IU/일

과량 시 출혈 경향

Recommended Feeding Dosage Guide

The appropriate dosage of quercetin varies depending on the product’s concentration, your pet’s weight and health status, and the presence of any underlying conditions. Currently, there is no single, standardized veterinary recommendation for dosing. Because cats and dogs differ in their liver metabolism, especially cats, it’s important to start with a much lower dose than for dogs and closely monitor their response. Since quercetin has low bioavailability, administering it with a meal containing fat may improve absorption. Ingredient concentrations vary by product, so always check the label. For safety, consult your veterinarian to determine the correct dosage and frequency based on your pet’s weight and overall health.

Side Effects and Situations to Watch Out For

Quercetin is generally considered a relatively safe ingredient, but there are important precautions to keep in mind when administering high doses over the long term.

Gastrointestinal issues: Vomiting, diarrhea, and decreased appetite may occur, especially when given on an empty stomach.

Kidney strain: Caution is advised when giving high doses of supplemental ingredients to pets with compromised kidney function.

Drug interactions: There is a potential for interactions with prescription medications. You must always inform your veterinarian of all medications currently being administered.

Pregnancy and lactation: Due to insufficient safety data, it is best to avoid use during these periods.

Combination of antioxidants: When administering multiple antioxidant ingredients simultaneously at high doses, consider the potential for cumulative burden on the body.

An image of a pet owner carefully giving a supplement to their puppy.

Do Not Use in These Pets

Breeds with known drug-sensitivity gene (MDR1/ABCB1) mutations, such as Collies, Shetland Sheepdogs, and Australian Shepherds, require careful consideration even when using supplemental ingredients like quercetin. Pets diagnosed with liver or kidney disease should also avoid high doses of supplements. Particular caution is needed when administering high-dose antioxidants to pets undergoing cancer treatment, due to concerns that antioxidants may interfere with the efficacy of cancer therapy. Caution is also advised when giving various supplements during the pre- and post-operative periods. If your pet is already taking steroids or immunosuppressants, do not add supplements on your own; instead, share a list of all current supplements with your veterinarian before making any decisions.

How to Feed for Better Effectiveness

Consistency is key when using quercetin. Try following these steps:

Step 1 — Start with a low dose: Begin with half the recommended amount and administer it for 3–5 days while monitoring your pet’s response.

Step 2 — Give with meals: Administering quercetin alongside a meal containing fat and protein may enhance absorption.

Step 3 — Regular assessment: Keep a weekly record of itching and scratching frequency to share with your veterinarian.

Step 4 — Consider combinations: You may explore combining quercetin with supportive ingredients like omega-3 fatty acids or probiotics, but always consult your veterinarian to determine the efficacy and safety of such combinations.

Step 5 — Periodic re-evaluation: For long-term use, it is advisable to periodically reassess the necessity and dosage with your veterinarian.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can I share human quercetin supplements with my dog?

Even if the base ingredients are the same, human products may contain xylitol, caffeine, or excessive vitamins, which can be dangerous for pets. Always use products specifically formulated for animals, or if using a human product, consult your veterinarian to verify the ingredients and calculate the appropriate dose based on your pet's weight.

When will I start seeing results?

Supplements typically take time to show results. Rather than expecting dramatic improvements in a short period, it’s more practical to track your pet’s symptoms on a weekly basis and evaluate progress together with your veterinarian.

I heard it contains onions. Is it safe to feed onions to my pet?

Absolutely not. While onions are rich in quercetin, they also contain toxic compounds that can damage your pet’s red blood cells and lead to anemia. Quercetin should only be given in purified supplement form.

Can I use this on my cat too?

While it can be used, start with a much lower dose than for dogs, and always consult your veterinarian first. Cats may be sensitive to plant-based ingredients due to a deficiency in certain liver metabolic enzymes. The appropriate dosage should be determined by your veterinarian based on your cat’s weight and health status.

Can it be used together with other allergy medications?

While it may be used alongside specialized medications like Apoquel or Cytopoint, there is a potential for interactions with immunomodulators and steroids. For safety, please share your list of supplements with your veterinarian before making any decisions.