{"id":192763,"date":"2023-11-03T11:47:23","date_gmt":"2023-11-03T09:47:23","guid":{"rendered":"https:\/\/fendaf.ee\/uncategorized-et-en\/kvertsetiin-ja-allergiad\/"},"modified":"2026-11-14T03:30:04","modified_gmt":"2026-11-14T01:30:04","slug":"kvertsetiin-ja-allergiad","status":"publish","type":"post","link":"https:\/\/fendaf.ee\/en\/health\/kvertsetiin-ja-allergiad\/","title":{"rendered":"Quercetin and allergies: can a natural antihistamine help dogs?"},"content":{"rendered":"

When a dog keeps scratching, licking its paws or returning to the vet with ear problems, the conversation often turns quickly to allergies. But does itching always mean an allergy? Not at all. Fleas, an overgrowth of yeast, bacterial skin inflammation or several problems together may be responsible. That is why I don’t want a new supplement to become yet another reason to postpone finding the real cause.<\/p>\n

Quercetin is often described as a natural antihistamine, and it is an interesting substance. It occurs in everyday fruit and vegetables, laboratory research has identified effects on pathways involving inflammation and histamine, and a few studies have involved dogs. But these three facts cannot simply be treated as interchangeable. Let’s look at what quercetin may mean for dogs and when it could be a sensible additional option.<\/p>\n

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Before quercetin: why is the dog itching?<\/h2>\n

With an allergy, the immune system reacts to a substance in food or the environment in a way that causes symptoms. In dogs these often show up on the skin: itching, paw licking, recurring ear inflammation or redness. An adverse reaction to food may cause both skin and digestive symptoms. But the same visible signs can arise for entirely different reasons.<\/p>\n

Research on canine food allergies most frequently identifies beef, dairy products, chicken and wheat. Soy and corn are also recognised food allergens in veterinary sources, although they appear less frequently in reviews of confirmed cases. For an individual dog, what matters is which proteins it has encountered and which ones trigger a reaction. A food allergy cannot be diagnosed from an ingredient list alone. When indicated, a controlled elimination diet followed by a food challenge is used. In cases of environmental allergies, secondary skin and ear infections also need attention.<\/p>\n

I have written on FendaF before that not every itch is an allergy. An overgrowth of Malassezia<\/em> yeast, for example, can cause intense itching in its own right. Distinguishing these problems matters because quercetin does not replace treatment directed at the underlying cause of a yeast or bacterial infection. Our article on yeast infections in dogs explores this in more detail.<\/p>\n

What exactly is quercetin?<\/h2>\n

Quercetin is a plant polyphenol belonging to the flavonol group. It occurs in apples, onions, berries, cherries and various herbs. One important distinction: some human foods rich in quercetin, such as onions, are toxic to dogs. We cannot choose food for a dog on the basis of one beneficial molecule alone.<\/p>\n

In cell and test-tube studies, quercetin has influenced mast-cell activity, processes associated with histamine release and inflammatory signalling pathways. This is where the nickname \u201cnatural antihistamine\u201d comes from. But conventional antihistamine medicines block a particular histamine receptor. Quercetin’s potential actions are more complex, and its use in dogs does not have the same clinical evidence base.<\/p>\n

That does not make the mechanism irrelevant. It means we must distinguish a reaction observed in a laboratory from whether an itchy dog actually scratches less after taking a supplement. One does not automatically prove the other.<\/p>\n

What do the studies in dogs actually show?<\/h2>\n

In 2010, Reinboth and colleagues studied the absorption of different forms of quercetin in nine adult beagles. Under one set of test conditions, absolute oral bioavailability was about 4%. Isoquercitrin was absorbed roughly one and a half times better than free quercetin in the same comparison, while the relative absorption of rutin was not worse than that of free quercetin. The study helps explain why formulation matters. It did not assess allergic itching or demonstrate a treatment effect.<\/p>\n

In 2023, researchers investigated a supplement containing quercetin, bromelain and components from shiitake mushrooms in kennel dogs. They measured, among other things, faecal inflammatory markers and other physiological indicators. A subsequent 2024 paper investigated the effect of the same combination on the gut microbiome of healthy dogs. These findings are interesting, but they do not establish that quercetin alone treats canine allergies. Healthy study dogs are not automatically comparable to patients with chronic atopic dermatitis.<\/p>\n

Special diets containing polyphenols have also been studied in dogs. If a formula contains several fatty acids, antioxidants and other ingredients and skin condition improves, the result cannot be attributed to a single molecule without appropriate controls. For now, the narrower conclusion is more reasonable: quercetin affects inflammatory mechanisms worth investigating, but a reliably established canine treatment protocol for allergic itching is still lacking.<\/p>\n

Could quercetin still form part of an overall plan?<\/h2>\n

Integrative veterinarians sometimes consider quercetin as one possible supportive option. Dogs Naturally, for instance, has called it \u201cnature’s Benadryl\u201d. The comparison is understandable, but I would not interpret it as a promise that a capsule replaces allergy medication. A dog with severe itching and broken skin should not have to suffer for weeks while we wait to see whether a supplement works on its own.<\/p>\n

A more comprehensive approach starts by identifying what is maintaining the problem: parasites, yeast, bacteria, food allergies, environmental factors or a damaged skin barrier. Then we can consider skin care, suitable nutrition, omega-3 fatty acids, veterinary medication where needed and, in some cases, a supplement. The real question is not \u201cnatural or pharmaceutical?\u201d but what will safely help this particular dog.<\/p>\n

From food or from a supplement?<\/h2>\n

Starting with everyday food is straightforward. A small piece of apple without seeds, a few dog-safe berries or a little parsley can add variety to the diet of many healthy dogs. Treats and extras should generally account for no more than one tenth of daily energy intake, so that complete food remains the foundation. That ten per cent refers to calories, not weight or a therapeutic dose of quercetin.<\/p>\n

However, the amount obtained from food is usually much smaller than a concentrated capsule contains. We should not expect a few apple pieces to work like a clinical allergy treatment. Nor can we claim that quercetin from fruit is always absorbed better in dogs than every supplement formulation. The dog study described above showed that chemical form can substantially affect absorption.<\/p>\n

Some integrative veterinarians have recommended adapting the dose of human supplements to a dog’s weight. In reality, that is not entirely appropriate. Metabolism, formulation and interactions cannot be reduced to a simple proportion. We need to know the amount and form of the active substance, the other ingredients and any medicines the dog already takes. Human supplements may contain substances unsuitable for dogs, so dog-specific products are preferable.<\/p>\n