Allergies are one of the most common health issues that affect our dogs. Countless dog owners are doing their best to battle this problem and increase their dog's quality of life. Skin allergies, food allergies, and respiratory allergies are becoming so common that many puppies are already genetically predisposed to them. As most traditional veterinary treatments include strong medication with many potential adverse effects, holistic veterinarians lean toward gentler and more natural approaches.
Quercetin is a natural pigment found in a variety of colorful fruits and vegetables, such as apples, broccoli, berries, and more. This pigment (also known as flavonoid) is a powerful antioxidant that is blowing away scientists worldwide and making us wonder: could this be the allergy relief, so many dogs need and deserve?
While traditional veterinary medicine focuses mainly on curing the symptoms, holistic veterinary medicine focuses more on healing the cause. Both have their place, and both can help our dogs, but when we're talking about allergies, it's almost impossible to help our dogs long-term without approaching the issue holistically. Most dog owners don't know how allergies develop in the first place, which is why we become so fixated on our dog's symptoms – we just want the scratching to go away, but we're missing the complete picture.
Allergies arise as a combination of genetic and environmental factors. The immune system perceives a non-threatening substance in the environment as dangerous and responds to it by releasing an inflammatory chemical called histamine into the blood, which results in an allergic reaction. The most noticeable symptoms often include diarrhea and vomiting or itchy skin with visible changes (redness, bumps, hair loss, etc.).
Inflammation is one of the biggest underlying reasons why allergies manifest in dogs. It is closely tied to free radicals – unstable molecules that cause cell damage, which leads to an inflamed state in the body and (through that) a variety of different health problems, including allergies. Now that we know how allergic reactions happen, it becomes clear that the path to healing lies in finding a way to lower the inflammation in our dog’s bodies.
To lower the inflammation in the body and prevent allergic responses, the unstable free radicals have to get neutralized. That's where antioxidants come in! They bind to the free radicals and rob them of their destructive power. Quercetin is a potent antioxidant with anti-inflammatory, antiviral, and antiallergic effects.
Quercetin has been the focal point of many studies in recent years, so there is a lot of scientific research available to support these claims. A study on rats showed that quercetin was able to stop peanut-induced anaphylaxis (a severe and potentially fatal allergic reaction) by lowering the levels of histamine in their blood. The rats were receiving 50mg of quercetin per kilogram of body weight over the course
of four weeks. The researchers concluded that the longer period of time is crucial to see the results on a cellular level and that quercetin should seriously be considered as alternative medicine in preventing allergic attacks. They also noted that quercetin showed no toxicity to internal organs.
Another study looked at mice with atopic dermatitis caused by house dust mites. Quercetin successfully repressed the inflammation and even helped improve the condition of the affected skin! A human study gave the same results – participants with atopic dermatitis received quercetin orally for 15 days, which was enough for quercetin to reduce the severity of dermatitis and calm the inflammation. The number of dogs struggling with atopic dermatitis is higher every year, so these results are incredibly significant and offer hope for the thousands of dogs battling allergic inflammation every day.
It’s important to note that quercetin is not a superstar only in the realm of allergies; as an antioxidant, it has a multitude of other health benefits as well! Several studies have proven that quercetin can stop the growth of cancer cells or eliminate them entirely in various internal organs. Cancer is the most common cause of death in dogs, killing millions of dogs every year, which makes this research on quercetin not just necessary, but urgent. Quercetin has successfully reduced cancer cells in the lungs, bladder, liver, adrenals, prostate, ovaries, and more!
Quercetin is generally considered safe and not toxic to animals, even when taken in higher doses. There are, however, a few exceptions to this rule. Quercetin is not recommended for pregnant and breastfeeding dogs because there is currently a lack of research on whether it’s safe for unborn and newborn puppies. If your dog has kidney problems, it’s best to avoid quercetin too.
It is also not recommended to start supplementing your dog’s diet with quercetin if they are taking any medication without first consulting with your holistic vet. Quercetin interacts with many different medications – antibiotics, cyclosporine, diabetes medication, blood pressure medication, and medication that is broken down by the liver. Quercetin can change the effectiveness of these medications, so it’s crucial that a professional is overseeing the changes you are making in your dog’s daily diet.
Quercetin can only be effective as a supplement if it has good bioavailability – meaning, it has to actually make it into the circulation rather than being eliminated through metabolism. Quercetin has low bioavailability because of weak absorption and fast metabolism, but thankfully there are ways to improve its absorption!
Ideally, the supplement you buy will include certain added ingredients that increase the absorption of quercetin. Look for things such as vitamin C and bromelain, a natural digestive enzyme that gives the immune system an extra boost when paired with quercetin. Another factor of good absorption is the correct dosage. A study on rats found that 20% of quercetin was absorbed when administered orally, but another study involving dogs showed only 4% of quercetin reaching circulation.
The study on dogs involved a much lower dose, one that matched commercial quercetin-supplemented dog food. It's important to acknowledge that dogs have the digestive system of a carnivore, so they can't metabolize plant pigments very well. Their large intestine is very short; it eliminates plants before the absorption can occur. Researchers recommend that you split your dog's daily quercetin dose into two or three parts, as this will ensure the consistent presence of quercetin in your dog's system.
Quercetin supplements come in the form of capsules and pills, so read their instructions carefully and follow the dosage guidelines, as they may vary between different products. Your dog's specific dose will depend on its size and the severity of its allergic condition. Start with the lowest recommended dose and then slowly raise it if you think your dog needs more support.
A holistic veterinarian's recommendation is 125 mg of pure quercetin per day for small dogs (up to 20 lbs), 250 mg per day for medium-sized dogs (25 to 50 lbs), and 375 mg per day for large dogs (50 lbs and more). Remember that quercetin will need some time to start working, so be patient and wait a couple of weeks before you make changes to the dose. Most research indicates that the first results should be visible between two to four weeks.
Thanks to the abundance of research, it is clear that quercetin not only “has potential” to reduce allergic inflammation but can actively do so when given at an appropriate dose alongside compounds that increase its bioavailability. However, it is definitely not a quick cure and will likely have to be supplemented long-term, on which we don't have any studies yet.
Hopefully, more research is coming in the next few years, especially on the effects of long-term supplementation. Still, even with the information we have so far, it's clear that scientists, holistic veterinarians, and the canine wellness market are all championing this natural pigment and giving it their stamp of approval.
Raman, Ryan. “What Is Quercetin? Benefits, Foods, Dosage, and Side Effects.” Healthline, 01/07/2020.
Mlcek, Jiri. Jurikova, Tunde. Skrovankova, Sona. Sochor, Jiri. “Quercetin and Its Anti-Allergic Immune Response.” MDPI, 12/05/2016.
Shishehbor, Farideh. Behroo, Lotfollah. Broujerdnia, Ghafouriyan Mehri. Namjoyan, Forough. Latifi, Seiyed-Mahmoud. “Quercetin Effectively Quells Peanut-Induced Anaphylactic Reactions in the Peanut Sensitized Rats.” Iranian Journal of Allergy, Asthma and Immunology, 03/2010.
“Quercetin.” Medline Plus.
Karuppagounder, Vengadeshprabhu. Arumugam, Somasundaram. Thandavarayan, A. Rajarajan. Sreedhar, Remya. Giridharan, V. Vijayasree. Watanabe, Kenichi. “Molecular targets of quercetin with anti-inflammatory properties in atopic dermatitis.” Science Direct, 04/2016.
Reinboth, Marianne. Wolffram, Siegfried. Abraham, Getu. Ungemach, R. Fritz. Cermak, Rainer. “Oral bioavailability of quercetin from different quercetin glycosides in dogs.” Cambridge University Press, 16/03/2010.
Krause, Angie. “5 Supplements EVERY Itchy, Allergic Dog Should Be Taking.” Boulder Holistic Vet.
Luna’s passion for learning about canine psychology and behavior began when she adopted a severely reactive puppy from a local shelter. She is now a big advocate for positive reinforcement and compassionate training. As a writer, she strives to spotlight the topics that fly under the radar and be the voice for all who cannot speak for themselves.