Quercetin for Allergies: Strong in Mice, a Handful of Small Human Trials
Quercetin is sold as a natural antihistamine. The animal data are consistent, but human trials are few and small, and the largest was paid for by the ingredient's maker.
By Kymata Health Editorial Published Last checked
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Key takeaways
From 9 sources- A 2025 narrative review of recent research counted only 2 clinical trials of quercetin on its own for allergic disease; other trials tested multi-ingredient products5.
- In 66 Japanese adults with pollen allergy, 200 mg/day of quercetin as a phytosome for 4 weeks improved several eye and nose symptom scores versus placebo1.
- That trial was commissioned and paid for by Indena, which supplied the quercetin phytosome tested1.
- Two small Japanese trials of a modified quercetin glycoside (EMIQ) found lower eye-symptom scores during cedar pollen season, without a clear nasal benefit23.
- Animal studies show consistent drops in IgE and histamine, but those results come from mice and rats4.
- There are no adequate safety data for more than 12 weeks at 1,000 mg/day or more6.
What this article covers
1 evidence profileThe evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
1 row- BGrade BSystolic and diastolic blood pressureImproved Quercetin lowered systolic blood pressure by 2.38 mmHg overall and by 1.82 mmHg in people with normal blood pressure, and lowered diastolic pressure by 3.14 mmHg in people with elevated or high blood pressure.Quercetin · Meta-analysis · n=841 · 2022 · PMID 35948195
The 'natural antihistamine' idea
In lab research, quercetin blocks mast-cell degranulation and reduces histamine release, the chain of events behind sneezing and itchy eyes5.
A 2025 meta-analysis of 13 rodent studies found quercetin lowered total IgE, allergen-specific IgE and histamine, and reduced immune-cell infiltration4. The authors noted large differences between studies and said well-designed human trials are needed before clinical use4.
What the human trials found
The largest single-ingredient trial randomized 66 Japanese adults aged 22 to 78 with pollen-allergy symptoms to a quercetin phytosome providing 200 mg/day of quercetin, or placebo, for 4 weeks1. Several questionnaire scores improved more than with placebo, including eye itching, sneezing, runny nose and sleep problems1.
Two trials from Osaka tested enzymatically modified isoquercitrin (EMIQ), a modified form of quercetin, during Japanese cedar pollen season23. In 20 people taking EMIQ or placebo for 8 weeks, total eye-symptom and eye-itching scores were lower than placebo across the season, while nasal scores only trended lower2.
In 24 people who started EMIQ 4 weeks before pollen release, the combined eye-symptom and medication score was lower than placebo, but nasal symptoms did not differ3. Neither EMIQ trial significantly lowered blood IgE23.
Who ran the trials
The 66-person trial was conducted under assignment from Indena Japan and Indena S.p.A. at their cost, Indena supplied the test and placebo products, and one author lists an Indena Japan affiliation1. Indena also paid for editorial assistance on the paper, and the authors declared no conflict of interest1.
Many allergy products blend quercetin with other ingredients. In a trial of 146 children, a blend of perilla, quercetin and vitamin D3 added to antihistamines lowered total symptom scores about as much as placebo after 4 weeks (63.6% versus 60.7%), although fewer children worsened on the blend (8 versus 16)7.
Doses and forms
The largest trial used 200 mg/day of quercetin from a phytosome1, while the Osaka trials used EMIQ, a modified quercetin glycoside2. Supplements are often sold at up to 1,000 mg a day, above usual dietary intake6. Absorption differs a lot by form; see quercetin forms and absorption.
Quercetin's better-supported effect is elsewhere
Quercetin's most consistent human finding is a small drop in blood pressure: systolic pressure fell by 2.38 mmHg across 10 trials8. That evidence is covered in quercetin and blood pressure.
Safety and who should be careful
A review by Germany's Federal Institute for Risk Assessment found adverse effects were rarely reported in human studies and were mild6.
Who should be careful:
- Anyone on prescription drugs: short-term human and animal studies found quercetin can change the bioavailability of certain drugs6. It acts on several CYP450 drug-metabolizing enzymes and on the drug transporter P-glycoprotein; a 2026 systematic review found clinically significant interactions shown so far for only a few drugs, mainly ones handled by CYP2C9, CYP2E1 or P-glycoprotein9. Check with a pharmacist first.
- People with kidney disease: animal studies suggest quercetin could worsen toxic effects in an already damaged kidney6.
- People with oestrogen-dependent cancer: animal studies raised the possibility that quercetin could promote tumour growth6.
- Long-term high doses: there are no adequate safety data beyond 12 weeks at 1,000 mg/day or more6.
- People with asthma or severe allergies: quercetin has not been tested as a replacement for antihistamines, nasal steroids or emergency medicines.
Quick answers
Common questions
4 answersHow much quercetin was used in allergy trials?
The 66-person trial used 200 mg/day of quercetin from a phytosome for 4 weeks1.
Is quercetin a natural antihistamine?
It lowered histamine in animal studies4, but none of the human trials in our sources tested it head to head with an antihistamine drug.
Does it help to start quercetin before allergy season?
One EMIQ trial started 4 weeks before pollen release and found lower eye scores, but no difference in nasal symptoms3.
Are quercetin blends with vitamin C or bromelain better?
None of the trials in our sources tested quercetin with vitamin C or bromelain. The one blend trial, of perilla, quercetin and vitamin D3 in 146 children, found symptom scores fell about as much as with placebo7.
Keep reading
Full evidence profiles
Every graded study, studied doses, interactions and safetyRelated articles
4 articles- ArticleQuercetin and Blood Pressure: A Real but Small Drop of About 2 to 3 mmHgDoes quercetin lower blood pressure?
- ArticleQuercetin Phytosome vs Plain Quercetin: Absorption Differs up to 62-FoldIs quercetin phytosome better absorbed than regular quercetin?
- Article400 IU of Vitamin E Is Either 268 mg or 180 mg. The "d" or "dl" on the Label DecidesHow many mg is 400 IU of vitamin E, and is natural better than synthetic?
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2 capsules: 1,000 mg quercetin (QU995, 99.5% anhydrous quercetin); 30 servings
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1 vegetarian capsule: 150 mg quercetin; 90 servings
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References
9 sources. Numbers in the text link here.
Sources cited in this article
9 sources- 1Effects of repeated oral intake of a quercetin-containing supplement on allergic reaction: a randomized, placebo-controlled, double-blind parallel-group studyEur Rev Med Pharmacol Sci, 2022 · PMID 35776034
- 2Effect of enzymatically modified isoquercitrin, a flavonoid, on symptoms of Japanese cedar pollinosis: a randomized double-blind placebo-controlled trialInt Arch Allergy Immunol, 2009 · PMID 19295240
- 3Preventative effect of a flavonoid, enzymatically modified isoquercitrin on ocular symptoms of Japanese cedar pollinosisAllergol Int, 2009 · PMID 19454839
- 4Quercetin exhibits multi-target anti-allergic effects in animal models: a systematic review and meta-analysis of preclinical studiesFront Pharmacol, 2025 · PMID 41357894
- 5Quercetin and Its Lecithin-Based Formulation: Potential Applications for Allergic Diseases Based on a Narrative ReviewNutrients, 2025 · PMID 40362785
- 6Safety Aspects of the Use of Quercetin as a Dietary SupplementMol Nutr Food Res, 2018 · PMID 29127724
- 7A polycentric, randomized, double blind, parallel-group, placebo-controlled study on Lertal, a multicomponent nutraceutical, as add-on treatment in children with allergic rhinoconjunctivitis: phase I during active treatmentJ Biol Regul Homeost Agents, 2019 · PMID 30968678
- 8The Effects of Quercetin Supplementation on Blood Pressure - Meta-AnalysisCurr Probl Cardiol, 2022 · PMID 35948195
- 9Quercetin as a modulator of xenobiotic metabolism: integrating CYP450 regulation, phase II conjugation pathways, and transporter-mediated drug interactionsEur J Clin Pharmacol, 2026 · PMID 42827146
Quercetin and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. Product links on this page are paid partner links.