Quercetin

Flavonoid · also known as 3,3',4',5,7-pentahydroxyflavone

Dietary flavonoid reported to inhibit mast cell mediator release in laboratory models; randomised human trials exist in allergic rhinitis, none in MCAS.

How it relates to mast cells: Mast cells in the laboratory
Types of studies cited: Human mast cells in vitro
Randomised trials in: seasonal allergic rhinitis
Approved for: nothing — US dietary supplement — not FDA-approved as a drug

What this relationship means: Studied on mast cells directly, but in cell culture or animals rather than in people. The study-design field distinguishes human cells from non-human models. A mechanism demonstrated in a dish is a reason to investigate, not a result — and the concentrations used are frequently ones that human exposure does not reach.

Mechanism of action

Quercetin is a flavonoid present in many plant foods. In laboratory models it interacts with phosphatidylinositol-3-kinase and mitogen-activated protein kinase signalling — pathways that sit downstream of the high-affinity IgE receptor on mast cells — and the polyphenol literature describes it as reducing mediator release on that basis.

Two limits belong on this entry. The evidence is mechanistic: it comes from cell and animal models, not from human outcome data in this population. And quercetin’s oral bioavailability is poor, which is the reason the recent literature concerns itself with reformulation rather than with the plain compound — laboratory concentrations are not straightforwardly reachable by ingestion.

Sources

Effects of repeated oral intake of a quercetin-containing supplement on allergic reaction: a randomized, placebo-controlled, double-blind parallel-group study Peer-reviewed study 2022 PMID 35776034 · link checked 25 Aug 2026
Impact of polyphenols on mast cells with special emphasis on the effect of quercetin and luteolin Review article 2018 PMID 30799996 · link checked 20 Aug 2026
Quercetin and Its Lecithin-Based Formulation: Potential Applications for Allergic Diseases Based on a Narrative Review Review article 2025 PMID 40362785 · link checked 20 Aug 2026

What this evidence cannot establish

No human outcome data in MCAS supports this entry. Human trials do exist elsewhere — a randomised, placebo-controlled study in 66 adults with pollinosis is cited below — but they measured symptom scores in an allergic condition, not an effect on mast cells, so they do not establish an MCAS outcome or a measured mast-cell effect. The direct mast-cell support comes from cell and animal work: quercetin reduces calcium influx and mediator release in cultured mast cells. The exposure gap matters — in the LAD2 human mast cell line the effect comparable to dexamethasone required concentrations above 100 micromolar, and quercetin's oral absorption is poor and not reliably dose-related, which is why the recent literature is preoccupied with reformulation rather than with the plain compound.

What this page does not say

No dosing, and no claim that this works. The entry describes a published mechanism, the cited study types, and what those studies cannot establish — nothing further. Why the site is built this way.

Recently verified. Verified 25 Aug 2026