Quercetin: A natural anti-inflammatory and anti-histamine supplement for horses
One of the reasons I created the Nurture Equestrian website was to help me track the changes in my own horses health and try to map these to changes in grazing, management and environment. The goal is always to get better at managing C’s allergies and for my horse to live a happier, healthier life.
It’s really interesting to look back to early September when we moved the horses from the summer track to a rested paddock and the rain came and the grass grew like crazy. My September blog, focused on the role of Mast Cells, and how the sudden increase in potassium, nitrogen and protein in the rapidly growing (green) grass triggered the release of histamines by the bucket load, creating a super-itchy horse in just four days.
It’s the 1st of November now, and I moved my horses to their next new field four days ago. This is a field that has been rested since May, grew profusely in September/October and by anyone’s description is now lush. But there’s no itching. Why?
It’s always going to be a challenge to be scientific with a sample size of one. I can only comment on what I see right in front of me, and today, that’s a calm, happy horse who isn’t rubbing or scratching in anger.
What’s changed? Welcome Quercetin… my new (anti-inflammatory) hero!
What is Quercetin?
Quercetin is a flavonoid—a type of plant pigment found naturally in many fruits, vegetables, and plants. As one of the most abundant dietary flavonoids, quercetin belongs to a group of polyphenolic compounds known for their potent antioxidant and anti-inflammatory effects. Chemically, it works by stabilising mast cells, reducing histamine release, and modulating inflammatory pathways in the body.
Natural Sources of Quercetin
Horses can obtain quercetin from various dietary sources, though the concentrations vary significantly. Common sources include:
Fruits and Vegetables: Apples (particularly the skins), berries, citrus fruits, and leafy greens contain moderate amounts of quercetin. They’re also found in banana skins and back in September I trialled Equinutrive’s B-Complex for that reason.
However, the quantities found in these foods are generally considered insufficient to achieve therapeutic levels.
Botanicals: Buckwheat is one of the richest plant sources of quercetin. Other botanical sources include elderberry, hawthorn, and ginkgo biloba. I tried green tea for this reason too - although C didn’t like the resulting ‘brew’, so we gave up on that.
Supplemental Forms: Due to the relatively low concentrations in common feedstuffs, most therapeutic applications utilise quercetin supplements derived from concentrated plant extracts, particularly from Sophora japonica (Japanese pagoda tree).
Benefits for Horses
Research into quercetin's effects on equine health suggests in can help our horses in five key ways:
(1) Respiratory Support: Quercetin has demonstrated natural antihistamine properties that may help manage seasonal allergies and inflammatory airway conditions. A study published in the Journal of Veterinary Internal Medicine examined quercetin's effects on inflammatory markers in horses with recurrent airway obstruction (RAO), finding reduced inflammatory cytokines and improved respiratory parameters.
Read more about Inflammatory Airway Disease (IAD)
(2) As an Anti-Inflammatory: Research has shown that quercetin inhibits several inflammatory pathways. In equine studies, quercetin supplementation has been associated with reduced production of inflammatory mediators such as tumor necrosis factor-alpha (TNF-α) - a chemical messenger produced by the immune system that induces inflammation. and interleukin-6 (IL-6)- which regulates the inflammatory system during exercise. These effects may benefit horses with osteoarthritis, laminitis, or other inflammatory conditions.
(3) Exercise Recovery: Early research on quercetin supplementation in exercising horses suggests that adding quercetin creates improvements in antioxidant status and reduced markers of oxidative stress following intense exercise. This could mean there are benefits for performance horses experiencing exercise-induced inflammation.
Here’s an interesting comparison between horses and humans!
(4) Insulin Sensitivity: Emerging research indicates quercetin may help improve insulin sensitivity, which could benefit horses with equine metabolic syndrome (EMS) or insulin dysregulation. While more equine-specific research is needed, studies in other species show promising metabolic effects.
(5) Mast Cell Stabilisation: By stabilizing mast cells and reducing histamine release, quercetin may help horses with hives, insect bite hypersensitivity, and other allergic reactions. This mechanism makes it particularly valuable during spring and summer months when environmental allergens peak.
Read more about Quercetin and its Anti-Allergic Immune Response.
Bioavailability Considerations
From the reading I’ve done personally, it seems that pure quercetin has relatively poor absorption in the gastrointestinal tract. As a result, many equine supplements combine quercetin with bromelain (a pineapple-derived enzyme) or include it in phytosome form to enhance absorption. Supplements with quercetin seem to be more common in the US, but I’ll have to get reading more labels to be confident about its use in the UK.
Doseage
Now here is where it gets hard - as ever!
Like most supplements use for horses and humans, we need to dose higher than the average human - but how much? In hayfever season, I take 1 antihistamine a day and my 550kg horse takes 20 (in two doses of 10).
A human grade vegan Quercetin ‘high dose’ supplement seems to be 1000mg - taken as two tablets of 500mg. Reading around, I’ve seen recommendations from 250mg/day through to 6,000 - 8,000mg per day for acute cases!
Research suggests a minimum of 600mg to be effective in horses so that’s where I’ve started - with one 500mg tablet of Quercetin alongside my existing ‘handful’ serving of passion flower. When I run out of passion flower I’ll try it with just the quercetin tablet, and I imagine, I’ll be able to drop that off when my grass runs down and the mast cell stimulation is reduced.
I bought my human-grade quercetin from Amazon. Quick video below!
