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Quercetin

Herb ·Moderate evidence ·Reviewed May 2026

Plant flavonoid studied for allergy, blood pressure, and cardiometabolic markers. Human senolytic evidence comes from dasatinib plus quercetin combinations, not quercetin alone.

Evidence tier
Moderate
Indexed sources
21 2010–2026
Interactions
28
Cost / month
$4.50 budget
Read the sources → Compare profiles
What it's good for
  • Immune support16,17
  • Allergy relief13
  • Anti-inflammatory16,2
  • Cardiometabolic marker support7,4
  • Cardiovascular health
What to watch for
  • Headache
  • GI upset
  • Tingling sensation
  • Antibiotics (quinolones)
  • Cyclosporine

The bottom line

Evidence rating moderate. Most-documented uses: immune support, allergy relief, anti-inflammatory. 21 sources indexed (2010–2026), with 28 interaction records on file.

The science

How it works, mechanistically.

Core mechanism

Acts as an antioxidant flavonoid and may modulate mast cell activity and inflammatory signaling. Proposed zinc-ionophore and senolytic effects are mainly preclinical or combination-therapy findings, so quercetin-alone human effects are not established.16,2

Class
Flavonoid
Found in food
Onions, Apples, Berries
Low-status signs
Not applicable
Absorption
Water-soluble; take with food
Dosing

Dosing & protocol.

Common range
500–1,000 mg daily
Recommended form
Quercetin phytosome (enhanced bioavailability) or with bromelain

Poor bioavailability; take with bromelain or in phytosome form. Synergizes with vitamin C.3,4

Dosing protocol

Maintain · 500-1,000 mg/day

Often used seasonally during histamine or allergy flares.

No cycling requiredNo tolerance buildup
Forms

Forms & what to buy.

Ranked by evidence and value.

Quercetin Phytosome Recommended
Rank 1: phospholipid complex with best human bioavailability ranking. Head-to-head bioavailability or pharmacokinetic evidence supports this ranking (PMID: 40037045). Take with meals.
Premium250-500 mg/day
Liposomal Quercetin
Rank 2: lipid delivery intended to improve exposure. Product validation matters.
Premium250-500 mg/day
Quercetin Dihydrate
Rank 3: standard crystalline form. Poorly soluble, usually needs higher doses.
Budget500-1000 mg/day
Quercetin with Bromelain
Rank 4: combination formula. Bromelain adds enzyme support, not proven quercetin absorption for all products.
Mid500-1000 mg quercetin/day
Cost

What it actually costs.

Real-world pricing across three quality tiers. Assumes Quercetin Dihydrate.

BudgetBest value
$4.50 /mo
$0.15 per dose
Mid
$8.40 /mo
$0.28 per dose
Premium
$15.00 /mo
$0.50 per dose

Assumes about 500-1,000 mg/day. Liposomal or phytosome delivery systems explain most premium pricing in this category. Updated 2026-04-02.

From food

The same dose, as food.

How much you'd eat to match a supplemental dose.

500 mg quercetin
Several onions plus apples and capers

Capers are one of the richest food sources, but supplement-style intakes are still hard to reach daily.

100 mg quercetin
About 1 onion plus 1 apple

Food meaningfully contributes even when you do not supplement.

Goals

Goal-based dosing.

Seasonal allergies

Dose: 500-1,000 mg daily

Timing: Split morning and evening with meals

Often used as a mast-cell-supportive strategy rather than an acute antihistamine.

Exercise recovery

Dose: 500 mg daily4

Timing: With breakfast

Use consistently rather than expecting a single-dose effect.

Immune support

Dose: 500-1,000 mg daily16,17

Timing: With meals

Vitamin C and bromelain are common companion ingredients.

Lab work

Markers to track.

What to test, the optimal window inside the conventional range, and how long a response takes.

Systolic Blood Pressure SBP

Quercetin (500 to 1000 mg per day) lowers SBP by roughly 3 to 5 mmHg in meta-analyses, with larger effects in hypertensives.3,7

Optimal
105–120 mmHg
Conventional
90–120 mmHg
Responds in
BP responds within 4 to 8 weeks.

Pair with hsCRP since quercetin also modestly lowers inflammation. Phytosome and isoquercetin forms improve absorption.

hsCRPUric Acid

Uric Acid UA

Quercetin may modestly lower serum uric acid, with a small, dose-dependent effect that is clearest in people who begin with elevated (hyperuricemic) levels.1,2

Optimal
3.5–5.5 mg/dL
Conventional
3.5–7.2 mg/dL
Responds in
4 to 8 weeks

No fast strictly required, but avoid testing during an acute gout flare and within a few days of heavy purine intake (red meat, organ meats, alcohol, seafood). Hydration status and diuretic use confound results; retest under similar conditions.

hsCRPFasting GlucoseeGFRTriglycerides

Diastolic Blood Pressure DBP

Quercetin may produce a small reduction in diastolic blood pressure, with effects that are typically modest, dose-dependent, and clearest in people who start with elevated readings or higher doses (around 500 mg per day or more).3,7

Optimal
60–80 mmHg
Conventional
60–80 mmHg
Responds in
8 to 12 weeks

Measure after 5 minutes of seated rest, feet flat, arm supported at heart level, and avoid caffeine, exercise, and nicotine for 30 minutes beforehand. Use the average of 2 to 3 readings taken at the same time of day, and track a 1 to 2 week home average rather than a single clinic reading.

Systolic Blood PressurehsCRPResting Heart Rate

hsCRP

Quercetin is a flavonoid with antioxidant and anti-inflammatory properties, and some early trials suggest it may modestly lower hsCRP by dampening low-grade systemic inflammation (in part through reduced NF-kB signaling and cytokine production). The effect is preliminary and inconsistent: several studies show little to no change, and any reduction tends to be small and most apparent in people who start with elevated inflammation.2,16

Optimal
0–1 mg/L
Conventional
0–3 mg/L
Responds in
If a change occurs, it usually takes sustained daily use over roughly 6 to 12 weeks to show up on a repeat hsCRP test. Shorter courses are unlikely to register a meaningful shift.

hsCRP does not require fasting and is not sensitive to dose timing, so you can test at any time of day regardless of when you take quercetin. Because acute illness, recent injury, hard exercise, or infection can transiently spike the value far above any supplement effect, retest only when you feel well and have had no recent illness, and consider repeating the measurement a couple of weeks apart to confirm a trend rather than reacting to a single reading. A markedly high result points to acute inflammation rather than diet or supplements and should prompt a conversation with a clinician. If you are tracking hsCRP for cardiovascular risk or have a diagnosed inflammatory or metabolic condition, interpret results with your clinician; also flag quercetin use to them, since it can interact with some medications by affecting drug-metabolizing enzymes.

ESR (erythrocyte sedimentation rate)IL-6 (interleukin-6)Fibrinogen
Why people use it

Symptoms it's matched to.

Where this appears in the symptom-to-supplement map, ranked by relevance.

Seasonal allergies

84% relevance

Quercetin stabilizes mast cells and reduces histamine release; effect builds over weeks of consistent use.16,1

ImmuneModerate evidenceQuercetin phytosome or with bromelain, 500 to 1000 mg per day

Start 2 to 4 weeks before allergy season for prevention effect.

Chronic prostatitis / chronic pelvic pain syndrome (CP/CPPS) in men

82% relevance

Quercetin is a flavonoid with anti-inflammatory and antioxidant activity that reduced pelvic pain and symptom scores versus placebo in a small randomized trial of category III chronic prostatitis.

PainEmerging evidenceQuercetin 500 mg capsules taken twice daily, often paired with bromelain for absorption

Adjunctive only; human evidence is limited to small trials, so see a urologist for diagnosis and to rule out infection before relying on it.

Histamine intolerance

76% relevance

Mast cell stabilizer that reduces histamine release; clinically useful for histamine-driven symptoms.16,14

ImmuneModerate evidenceQuercetin phytosome, 500 to 1000 mg per day

Build up over 2 to 4 weeks for full effect.

Chronic sinus congestion

74% relevance

Quercetin is a flavonoid that may stabilize mast cells and reduce histamine release, potentially easing allergy-driven nasal congestion.1,2

ImmuneEmerging evidenceQuercetin, about 500 mg once or twice daily, sometimes combined with bromelain or vitamin C

Most relevant if congestion has an allergic component; take consistently rather than only as needed.

Chronic hives / urticaria

70% relevance

Quercetin may stabilize mast cells and reduce histamine release, which drives the wheals seen in urticaria, though human trial data is limited.1,2

ImmuneEmerging evidenceQuercetin, about 500 mg once or twice daily, often combined with vitamin C

An adjunct to, not a replacement for, antihistamines; give several weeks of consistent use.

Interstitial cystitis / bladder discomfort

68% relevance

Quercetin has anti-inflammatory and mast-cell-stabilizing actions that small studies suggest may ease pelvic pain in interstitial cystitis, though the evidence remains preliminary.1,2

ImmuneEmerging evidenceQuercetin phytosome

Interstitial cystitis is a chronic medical condition; use only alongside a urologist-directed plan as supportive care, never as a replacement.

Rosacea / facial redness

66% relevance

Quercetin may stabilize mast cells and dampen histamine release, which could help when flushing has a histamine-driven component, although direct rosacea data are sparse.1,2

AppearanceEmerging evidenceQuercetin phytosome

Phytosome or bromelain-paired forms improve the otherwise poor absorption of plain quercetin.

Gout / high uric acid

66% relevance

Quercetin inhibits xanthine oxidase in vitro and lowered plasma urate in a small human trial, suggesting a mild urate-lowering effect.16,18

PainEmerging evidenceQuercetin phytosome

Bioavailability is poor; phytosome forms or co-administration with vitamin C improve absorption.

Inflammation (general/chronic)

61% relevance

Quercetin helps calm mast-cell and inflammatory signaling.2,4

InflammationModerate evidenceQuercetin phytosome

Useful when histamine symptoms overlap.

Leaky gut / intestinal permeability

60% relevance

Quercetin is a flavonoid that may stabilize mast cells and support tight junction assembly in preclinical models, with limited human permeability data.1,2

DigestiveInsufficient evidenceQuercetin phytosome (or co-formulated with bromelain) for absorption

Bioavailability is low, so phytosome or co-formulated forms are preferred.

Asthma / bronchial support

60% relevance

Quercetin may stabilize mast cells and reduce histamine and inflammatory release relevant to allergic airway responses.16,1

ImmuneEmerging evidenceQuercetin, about 500 mg once or twice daily, often taken with vitamin C

Most relevant for allergy-driven asthma; human respiratory data is still preliminary.

Itchy skin / pruritus

60% relevance

Quercetin can stabilize mast cells and reduce histamine release in lab studies, which may help itch with an allergic component.2,1

AppearanceInsufficient evidenceQuercetin phytosome or quercetin with bromelain

Human itch data are limited; absorption is poor unless a bioavailable form is used.

Protocols

Featured in protocols.

Evidence-based stacks that include it, with the exact dose and timing each one uses.

Immunity Protocol

ImmunityOptionalModerate evidenceBeginner$20-35/mo
Dose here
500 mg
Timing
With food

Flavonoid studied for immune and inflammatory signaling; zinc-ionophore activity is mainly preclinical and should not be treated as proven antiviral benefit16,17

Chronic Inflammation Protocol

InflammationOptionalModerate evidenceIntermediate$35-60/mo
Dose here
500 mg
Timing
Twice daily

Mast cell stabilizer and NLRP3 inflammasome modulator; reduces hsCRP and supports inflammatory resolution.16,14

Allergy & Histamine Protocol

ImmunityCoreEmerging evidenceBeginner$30-50/mo
Dose here
500 mg twice daily (1,000 mg/day total)
Timing
With breakfast and with dinner, taken with food

Quercetin is a flavonoid shown in laboratory studies to help stabilize mast cell membranes, which may reduce degranulation and the release of histamine and other inflammatory mediators. Human clinical evidence for allergy symptoms is still limited and preliminary, so it is best viewed as supportive rather than a replacement for antihistamines.9,20

Sinus & Respiratory Support Protocol

ImmunityCoreEmerging evidenceBeginner$30-50/mo
Dose here
500 mg, once or twice daily
Timing
With meals

Quercetin is a flavonoid that may stabilize mast cells and modestly dampen histamine release and inflammatory signaling, which could offer supportive relief for airway and allergic irritation. Human respiratory and allergy evidence remains preliminary.14,16

Long COVID and Post-Viral Recovery Protocol

EnergyOptionalEmerging evidenceIntermediate$50-85/mo
Dose here
250-500 mg
Timing
With a meal, once or twice daily

Quercetin is a plant flavonoid with antioxidant and mast cell stabilizing activity in laboratory studies, which is why it has been explored for inflammatory and post-viral symptoms. The supporting human data are early and largely preclinical or observational, so treat it as an optional, exploratory addition.2,16

Eczema & Skin Barrier Protocol

Skin & HairOptionalEmerging evidenceBeginner$30-50/mo
Dose here
500 mg once or twice daily
Timing
With food

Quercetin is a flavonoid that in laboratory and cell studies helps stabilize mast cells and reduce histamine and inflammatory cytokine release, which are part of the itch and flare response in atopic skin. Human clinical evidence specific to eczema is limited and preliminary, so it is included as a supportive anti-inflammatory rather than a treatment.9,14

Safety

Full safety detail.

Side effects

  • Headache
  • GI upset
  • Tingling sensation

Contraindications

  • Antibiotics (quinolones)
  • Cyclosporine
  • May interact with CYP enzymes
Interactions

Interaction records.

InfoSynergy

Vitamin C

Quercetin and vitamin C have synergistic antioxidant effects. Vitamin C helps regenerate oxidized quercetin.

Recommendation: Take together for enhanced antioxidant and immune support.

InfoSynergy

Resveratrol

Quercetin inhibits resveratrol glucuronidation, increasing resveratrol bioavailability. Both are polyphenol antioxidants with complementary targets.

Recommendation: Take together. Quercetin may increase resveratrol bioavailability by inhibiting sulfotransferases and glucuronidases that metabolize resveratrol.

InfoSynergy

Turmeric/Curcumin

Both are potent anti-inflammatory polyphenols that modulate NF-κB and COX-2 through complementary mechanisms.

Recommendation: Take together for enhanced anti-inflammatory and antioxidant effects.

InfoSynergy

Vitamin C Liposomal

Quercetin and vitamin C have synergistic antioxidant effects. Vitamin C Liposomal helps regenerate oxidized quercetin.

Recommendation: Take together for enhanced antioxidant and immune support.

InfoSynergy

Curcumin Phytosome

Both are potent anti-inflammatory polyphenols that modulate NF-κB and COX-2 through complementary mechanisms.

Recommendation: Take together for enhanced anti-inflammatory and antioxidant effects.

InfoSynergy

Zinc

Quercetin has shown zinc-ionophore activity in cell models, but clinical immune benefit from combining quercetin with zinc is not established.

Recommendation: Do not rely on quercetin plus zinc as antiviral treatment. Use only as general nutrition support and keep zinc within standard supplemental limits unless clinician-directed.

ModerateCaution

Bee Pollen

Bee pollen naturally contains quercetin and related flavonoids, so adding a quercetin supplement increases total flavonoid intake and overlaps with bee pollen's own polyphenol load.

Recommendation: Account for the quercetin already present in bee pollen when adding a quercetin supplement, and note that both can trigger allergic reactions in sensitive individuals.

InfoSynergy

Olive Leaf Extract

Olive leaf polyphenols and quercetin are complementary antioxidant and anti-inflammatory flavonoids that may also additively support healthy blood pressure and endothelial function.

Recommendation: Reasonable to combine for antioxidant and vascular support; monitor blood pressure if also taking antihypertensives.

InfoSynergy

Green Tea Extract

Quercetin may raise plasma levels of green tea catechins by slowing their breakdown, and the two polyphenols provide additive antioxidant and anti-inflammatory activity.

Recommendation: Reasonable to take together for antioxidant support, with no special timing needed. Avoid stacking very high doses of multiple polyphenols if you have liver concerns.

InfoSynergy

Bromelain

Bromelain is traditionally co-formulated with quercetin to add anti-inflammatory activity, with the two compounds dampening inflammation through complementary routes.

Recommendation: Take together, ideally with food for tolerability. The pairing is standard for inflammatory and allergy support and needs no special timing.

InfoSynergy

Fish Oil

Quercetin and fish oil reduce inflammation through different pathways, giving an additive anti-inflammatory effect.

Recommendation: Reasonable to combine for cardiometabolic and anti-inflammatory support. Take quercetin with the fish oil meal, since dietary fat may aid quercetin absorption.

InfoSynergy

NAC

Quercetin and NAC provide complementary antioxidant support, with NAC replenishing glutathione and quercetin scavenging free radicals directly.

Recommendation: Reasonable to combine for antioxidant and respiratory or immune support, with no special timing required.

Search all 28 interaction records for Quercetin →

Sources

Sources, by evidence tier.

Numbered references. Citations throughout the page link here.

Meta-analyses & systematic reviews

12

Randomized controlled trials

3

Reviews & position papers

2
  • 16Quercetin and Its Anti-Allergic Immune ResponseNeeds reviewPMIDMlcek J et al. · Molecules · 2016

    Quercetin inhibits mast cell degranulation, reduces histamine and pro-inflammatory cytokines, and restores Th1/Th2 balance.

  • 17Quercetin and its anti-allergic immune response: a reviewNeeds sourceNo linkMlcek J, Jurikova T, Skrovankova S et al. · Molecules · 2016

Mechanistic & preclinical

2
  • 18Quercetin inhibits SARS-CoV-2 3CLpro activity: an in silico and in vitro studyNeeds sourceNo linkAbian O, Ortega-Alarcon D, Jimenez-Alesanco A et al. · Int J Biol Macromol · 2020
  • 19Quercetin reduces endothelial dysfunction and atherosclerosis in ApoE-knockout miceNeeds sourceNo linkLoke WM, Proudfoot JM, Hodgson JM et al. · J Nutr · 2010

Reference material

2
Keep exploring

Deep dives & adjacent profiles.

Goal hubImmune Support
Olive Leaf ExtractHerbChagaHerbVitamin C LiposomalVitaminVitamin CVitaminSeleniumMineralL-GlutathioneAmino Acid

This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.

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