Supplement analysis backed by scientific evidence · PT

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Limited evidenceImmunity

Allergy Support Formulas

Quercetin, nettle and bromelain combinations sold for hay fever. Each ingredient rests on a thin base of small trials, and the blends themselves have essentially never been tested as sold.

Evidence last reviewed: August 2026

What the science says

  • Quercetin and related polyphenols Limited evidence

    A systematic review and meta-analysis of polyphenolic compounds in allergic rhinitis found modest symptom improvement drawn from a small, heterogeneous set of trials. A separate randomized placebo-controlled trial of a quercetin supplement also reported reduced allergic symptoms.

  • Stinging nettle Limited evidence

    A randomized, double-blind, placebo-controlled trial of nettle root extract as supportive therapy for allergic rhinitis reported only partial benefit. The trial was small and the results mixed across outcomes.

  • Bromelain Limited evidence

    A systematic review of herbal medicines for rhinosinusitis identified only a few small studies of bromelain, insufficient to establish that it works.

Dosage & safety

Studied doseTypical blends supply 500–1000 mg quercetin, 300–500 mg nettle and 100–500 mg bromelain daily in divided doses. These amounts follow label convention, not trial protocols.
SafetyGenerally well tolerated. Bromelain can increase bleeding risk and interacts with anticoagulants, high-dose quercetin may interfere with drugs cleared by CYP3A4, and nettle can lower blood pressure and blood sugar. Not a substitute for antihistamines in significant allergy.

Scientific references

Where to buy

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