Quercetin

• Mast-cell and basophil stabilization — quercetin reduces degranulation and histamine release, so it acts like a natural mast-cell stabilizer. This is a central reason it may reduce immediate allergic symptoms. MDPI BioMed Central
• Inhibits inflammatory mediators — it blocks enzymes and signalling (e.g., lipoxygenase, some kinases, NF-κB pathways) that generate cytokines and leukotrienes involved in type-2 allergic inflammation. ScienceDirect
• Immune modulation (Th1/Th2 balance, IgE) — preclinical work shows quercetin can reduce antigen-specific IgE production and shift some immune responses away from a Th2-dominant allergic profile. BioMed Central Europe PMC
• Antioxidant effects — general anti-oxidative activity reduces tissue inflammation in allergic mucosa (nose, eye, gut). MDPI

Important caveat: most human clinical data are for allergic rhinitis, conjunctivitis, asthma (respiratory/ocular allergies). For food allergy / anaphylaxis the strongest positive evidence comes from animal and in-vitro studies (mouse/rat models), not large human trials — so application to true IgE-mediated food allergy in people remains experimental. Europe PMC ScienceDirect

Formulations used in trials

• Standard quercetin (aglycone) oral capsules — used in some trials at ~200 mg/day. European Review Examine
• “Phytosome” / lecithin-bound (bioavailable) formulations (e.g., Quercetin Phytosome / Quercefit) — these substantially increase absorption vs plain quercetin and are commonly used in trials/products; some studies used lower doses of phytosome forms because of improved bioavailability. If you take quercetin, a phytosome form improves blood levels. SpringerLink Indena

Doses and schedules (what trials actually used)

• 200 mg/day (oral) in a randomized, placebo-controlled trial for seasonal allergic rhinitis for 4 weeks — improvement in nasal/ocular symptoms and quality of life was reported. This is the most often-cited human RCT dose. European Review Examine
• 500 mg/day (bioavailable phytosome) for 2 weeks was used in a trial for allergic conjunctivitis and reported symptom improvement. Higher single doses (500 mg) are frequently used for ocular studies or when a phytosome product is used. Austin Publishing Group
• Other clinical reports and open-label studies used 100–800 mg/day depending on formulation and target (respiratory vs systemic trials); combinations with bromelain and vitamin C are commonly used in practice (bromelain may aid absorption/anti-inflammatory activity; vitamin C is an antioxidant companion), though that combination is supported mainly by mechanistic rationale and small clinical reports rather than large blinded RCTs. MedRxiv Europe PMC

How to take it (practical points)

• Take with food (fat improves absorption for many forms; phytosome versions are designed to be better absorbed). SpringerLink
• For seasonal complaints some trials started 4 weeks before pollen season and continued through the season — benefit may require days–weeks of consistent dosing. Human Clinical Studies
• If using to try to reduce allergic symptoms, common practical regimens in studies: 200 mg once daily (standard extract) or 500 mg once daily (bioavailable formulations) for several weeks. Clinicians often pair quercetin with vitamin C and/or bromelain, but that’s adjunctive and not a proven standard. European Review Austin Publishing Group

Summary: for respiratory/ocular allergy support, the best-documented human doses are ~200 mg/day (standard quercetin) and ~500 mg/day (bioavailable formulations) for short periods (2–8 weeks) in small trials. For food allergy there is no established clinical dosing — human evidence is lacking and use would be experimental. European ReviewAustin Publishing Group

Human clinical trials / systematic reviews

• Randomized, double-blind, placebo-controlled trial (Japan) — 200 mg/day, 4 weeks, allergic rhinitis: symptom and QOL improvements reported. (PDF summary / trial report). European Review Examine
• Conjunctivitis trial — 500 mg/day (Quercetin Phytosome), 2 weeks: reported relief of ocular symptoms and reduced need for anti-allergic meds. Austin Publishing Group
• MDPI review (2025) — Quercetin Phytosome and allergy review: summarized human and preclinical evidence and highlighted limited number and size of human trials, plus potential of phytosome formulations. MDPI
• Allergy, Asthma & Clinical Immunology review (2020): overview of quercetin’s anti-allergic properties, mechanisms and the state of evidence. Good for mechanistic background. BioMed Central

Preclinical / food-allergy–specific studies

• Mouse/rat models of food allergy / anaphylaxis — multiple animal studies show quercetin reduces histamine, reduces anaphylactic signs, and in some cases blocked peanut-induced anaphylaxis in mice (preclinical only). These are promising but not human-confirmatory. Example reviews and primary reports are summarized in the MDPI / Europe PMC articles. Europe PMC ScienceDirect

Pharmacokinetic / formulation studies

• Quercetin Phytosome bioavailability study — shows much higher plasma levels compared to unformulated quercetin; relevant because poor oral bioavailability is a limitation of standard quercetin. SpringerLink Indena