Quercetin
C15H10O7
A plant flavonoid with three connected rings and five hydroxyl (–OH) groups. Found in onions, apples, and capers.
Evidence current to September 2026
What it's pushed for
What the research shows
In the lab, quercetin blocked human mast cells from releasing histamine and other inflammatory chemicals.
In people, absorption is the problem: only about 1% of oral quercetin is absorbed. A 2025 review concluded well-designed human trials are still needed.
Safety looks reasonable at studied amounts. Human studies up to 12 weeks found it safe, and the FDA accepted it as generally recognized as safe (GRAS) for its intended use.
Myth vs. fact
Myth"Quercetin is a natural mast cell stabilizer."
FactIt stabilizes mast cells in a dish. Whether a typical capsule reaches high enough levels in your body to do the same hasn't been established.
Who should check with a clinician first
Anyone on multiple prescription medications. Ask a pharmacist about drug-metabolism interactions.
What to look for on the label
Look for an absorption-enhanced form, such as phytosome or lecithin-based, since plain quercetin is poorly absorbed.
How to read any supplement labelSources
This guide is for education, not medical advice. Supplements can interact with medications and health conditions. Talk with your clinician or pharmacist before starting, stopping, or changing anything. The Lily Perspective earns no income from any supplement brand or retailer.