Quercetin side effects: what 1,217 FDA adverse event reports show

Quercetin · 50 reaction terms · 414 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Who reports

1,217 reports · 51% serious · 34 with death outcome · 71% female

openFDA FAERS counts, all years, deduplication not applied

Used for

For temporary relief of swelling, fatigue, hay fever, mood swings, tendency to bruise easily, and drowsiness.

FDA label, Indications and Usage

Boxed warning

None in the current label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 16 strongest signals

Reporting / coding artifact 3Lab value / disease marker 1No label text to screen 12

What the badges mean

Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
No label text to screen No validated FDA label was retrievable for this product, so the screen could not run. Disproportionality only.

Strongest disproportionality signals

Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 34 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Brain fog	14	16.5 9.8–27.8ROR 16.7 · χ² 189 / p 3e-43	15.6 EB05 9.2 · IC025 +2.5 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 20.7	no trial data cached
Seasonal allergy	11	13.4 7.4–24.1ROR 13.5 · χ² 114 / p 6e-27	11.7 EB05 6.1 · IC025 +2.1 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious n=6	no trial data cached
Anaphylactic shock	16	10.7 6.6–17.5ROR 10.9 · χ² 132 / p 9e-31	9.4 EB05 5.8 · IC025 +2.2 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 12.3	no trial data cached
Blood pressure abnormal	10	8.7 4.7–16.1ROR 8.7 · χ² 60 / p 4e-15	6.8 EB05 3.8 · IC025 +1.6 3/3 methods agree	Lab value / disease marker	serious PRR 13.0	no trial data cached
Drug ineffective for unapproved indication	28	8.6 6.0–12.4ROR 8.8 · χ² 182 / p 1e-41	7.9 EB05 5.6 · IC025 +2.3 3/3 methods agree	Reporting / coding artifact	serious PRR 18.1	no trial data cached
Ageusia (loss of taste)	11	7.6 4.2–13.6ROR 7.6 · χ² 56 / p 3e-14	6.0 EB05 3.5 · IC025 +1.5 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 13.8	no trial data cached
Intentional dose omission	12	7.5 4.3–13.2ROR 7.6 · χ² 62 / p 2e-15	6.1 EB05 3.7 · IC025 +1.6 3/3 methods agree	Reporting / coding artifact	serious PRR 10.3	no trial data cached
Angioedema (deep swelling of face/throat)	19	7.4 4.7–11.6ROR 7.5 · χ² 99 / p 1e-23	6.4 EB05 4.3 · IC025 +1.9 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 8.9	no trial data cached
Product dose omission in error	11	7.0 3.9–12.7ROR 7.1 · χ² 51 / p 4e-13	5.6 EB05 3.3 · IC025 +1.5 3/3 methods agree	Reporting / coding artifact	serious PRR 14.4	no trial data cached
Panic attack	14	6.6 3.9–11.1ROR 6.7 · χ² 61 / p 3e-15	5.5 EB05 3.5 · IC025 +1.6 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 8.6	no trial data cached
Mood swings	12	6.5 3.7–11.3ROR 6.5 · χ² 50 / p 7e-13	5.3 EB05 3.2 · IC025 +1.4 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 12.9	no trial data cached
Throat tightness	10	6.4 3.4–11.8ROR 6.4 · χ² 40 / p 1e-10	5.1 EB05 2.9 · IC025 +1.3 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 5.2	no trial data cached
Hot flush (hot flashes)	24	5.5 3.7–8.1ROR 5.6 · χ² 84 / p 3e-20	5.0 EB05 3.5 · IC025 +1.6 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 5.3 · 95% consumer	no trial data cached
Eye irritation	15	4.6 2.8–7.6ROR 4.7 · χ² 39 / p 2e-10	4.1 EB05 2.7 · IC025 +1.2 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 14.1	no trial data cached
Dermatitis atopic	12	4.1 2.3–7.2ROR 4.2 · χ² 25 / p 2e-7	3.6 EB05 2.2 · IC025 +0.9 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious n=1	no trial data cached
Injection site swelling	10	2.3 1.2–4.2ROR 2.3 · χ² 6 / p 0.008	2.1 EB05 1.3 · IC025 +0.0	No label text to screen label has no adverse-reaction text	serious PRR 6.7	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

Most frequently reported reactions

By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Drug ineffective for unapproved indication	28	8.6 6.0–12.4ROR 8.8 · χ² 182 / p 1e-41	7.9 EB05 5.6 · IC025 +2.3 3/3 methods agree	Reporting / coding artifact	serious PRR 18.1	no trial data cached
Hot flush (hot flashes)	24	5.5 3.7–8.1ROR 5.6 · χ² 84 / p 3e-20	5.0 EB05 3.5 · IC025 +1.6 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 5.3 · 95% consumer	no trial data cached
Angioedema (deep swelling of face/throat)	19	7.4 4.7–11.6ROR 7.5 · χ² 99 / p 1e-23	6.4 EB05 4.3 · IC025 +1.9 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 8.9	no trial data cached
Anaphylactic shock	16	10.7 6.6–17.5ROR 10.9 · χ² 132 / p 9e-31	9.4 EB05 5.8 · IC025 +2.2 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 12.3	no trial data cached
Eye irritation	15	4.6 2.8–7.6ROR 4.7 · χ² 39 / p 2e-10	4.1 EB05 2.7 · IC025 +1.2 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 14.1	no trial data cached
Panic attack	14	6.6 3.9–11.1ROR 6.7 · χ² 61 / p 3e-15	5.5 EB05 3.5 · IC025 +1.6 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 8.6	no trial data cached
Brain fog	14	16.5 9.8–27.8ROR 16.7 · χ² 189 / p 3e-43	15.6 EB05 9.2 · IC025 +2.5 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 20.7	no trial data cached
Dermatitis atopic	12	4.1 2.3–7.2ROR 4.2 · χ² 25 / p 2e-7	3.6 EB05 2.2 · IC025 +0.9 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious n=1	no trial data cached
Mood swings	12	6.5 3.7–11.3ROR 6.5 · χ² 50 / p 7e-13	5.3 EB05 3.2 · IC025 +1.4 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 12.9	no trial data cached
Intentional dose omission	12	7.5 4.3–13.2ROR 7.6 · χ² 62 / p 2e-15	6.1 EB05 3.7 · IC025 +1.6 3/3 methods agree	Reporting / coding artifact	serious PRR 10.3	no trial data cached
Product dose omission in error	11	7.0 3.9–12.7ROR 7.1 · χ² 51 / p 4e-13	5.6 EB05 3.3 · IC025 +1.5 3/3 methods agree	Reporting / coding artifact	serious PRR 14.4	no trial data cached
Ageusia (loss of taste)	11	7.6 4.2–13.6ROR 7.6 · χ² 56 / p 3e-14	6.0 EB05 3.5 · IC025 +1.5 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 13.8	no trial data cached
Seasonal allergy	11	13.4 7.4–24.1ROR 13.5 · χ² 114 / p 6e-27	11.7 EB05 6.1 · IC025 +2.1 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious n=6	no trial data cached
Injection site swelling	10	2.3 1.2–4.2ROR 2.3 · χ² 6 / p 0.008	2.1 EB05 1.3 · IC025 +0.0	No label text to screen label has no adverse-reaction text	serious PRR 6.7	no trial data cached
Throat tightness	10	6.4 3.4–11.8ROR 6.4 · χ² 40 / p 1e-10	5.1 EB05 2.9 · IC025 +1.3 3/3 methods agree	No label text to screen label has no adverse-reaction text	serious PRR 5.2	no trial data cached

Unlabeled candidate signals

Every screened signal with n ≥ 20 was either labeled, an indication term, or an artifact pattern — no unlabeled candidate stood out in the top signals.

Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.

Common questions

What are the most reported side effects of Quercetin?

In FDA FAERS, the most frequently co-reported reaction terms for Quercetin are hot flush, angioedema, anaphylactic shock, eye irritation, panic attack, brain fog. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.

Does Quercetin have an FDA boxed warning?

No. The FDA label retrieved for Quercetin has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Quercetin causes these side effects?

No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.

Sources & methods

FDA label via openFDA (set ID c2d4d260-9d53-4314-a9e1-a710cd00a27e, effective 20170228; matched on openfda.generic_name.exact:"QUERCETIN")
Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA count= aggregation, field patient.drug.openfda.generic_name.exact, 50 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction
Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
Seriousness and sex counts from openFDA count=serious, patient.patientsex, seriousnessdeath

Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.