TL;DR: Quercetin and vitamin C work together to stabilize mast cells, reduce histamine, and calm inflammation. Research suggests this natural combination may support people with seasonal allergies and asthma while promoting immune balance.

There are dozens of herbal and nutrient preparations that help allergy sufferers naturally. Almost every supplement company has its own formula. Many of these contain substances that lower histamine and reduce inflammation. One particularly powerful combination is quercetin and vitamin C.

Quercetin and Vitamin C: Potent Synergy

Quercetin is a flavonoid with antioxidant [1], anti-inflammatory, antiviral [2], and immunoprotective [3] properties. Its antioxidant power is enhanced by vitamin C [4]—the two nutrients work better together, as vitamin C helps recycle quercetin and prolong its activity in the body.

Allergies and Asthma

Quercetin has generated significant interest because of its potential to support people with allergies and asthma. Both in-vitro and in-vivo studies—using animals and human tissue—show promising effects.

  • In vitro, quercetin inhibited rat tracheal contractility at both presynaptic and postsynaptic sites, suggesting a possible role in airway disorders such as asthma [5].
  • Another animal study found that polyphenols such as gingerol, quercetin, and EGCG inhibited mucus hypersecretion in respiratory epithelial cells while maintaining normal ciliary motion [6].
  • Quercetin also decreased histamine and inflammatory markers, lowered phospholipase A2 activity, and reduced leukocyte recruitment in bronchoalveolar lavage fluid. Its anti-asthmatic activity was comparable to cromolyn sodium and dexamethasone [7].
  • Additional research showed that quercetin decreased IL-4, increased interferon-γ, and significantly reduced airway inflammation [8].
    Treated mice had thinner epithelial layers, less subepithelial muscle thickening, and fewer goblet and mast cells compared with untreated animals [9].
  • Other studies confirm similar anti-inflammatory and airway-protective effects [10–13].

Together, these findings indicate that quercetin can stabilize mast cells, reduce histamine release, and calm airway inflammation—mechanisms relevant to both allergic rhinitis and asthma.

Human Quercetin Studies

While more research is needed, existing human studies show encouraging results.

  • Quercetin supplementation has been shown to reduce inflammatory markers [14] and improve exercise endurance and VO₂ max [15] in healthy volunteers.
  • As an antioxidant and anti-inflammatory compound, quercetin has demonstrated benefits in a range of human conditions [16].
  • In women with rheumatoid arthritis, 500 mg/day for eight weeks led to significant improvements in clinical symptoms and inflammatory cytokines [17].
  • Other research suggests quercetin may help protect nerve cells in Parkinson’s disease [18], modulate mast-cell activity [19], and even exhibit anticancer properties [20–22].

The Role of Rutin

Rutin, another plant-derived flavonoid (commonly from buckwheat), acts as a powerful antioxidant and anti-inflammatory synergist.
It enhances quercetin’s effects and has shown additional benefits for metabolic, cardiovascular, and neurological health [23–25].

Summary

Quercetin and vitamin C together provide a natural, physiologic approach to allergy support.
By stabilizing mast cells, reducing histamine release, and calming airway inflammation, this combination helps support people with seasonal allergies, asthma, and inflammatory conditions—without the side effects of many medications.

Educational only — not medical advice. Work with doctors trained in natural healthcare.

FAQs:

Q: Can quercetin really help with allergies?
A: Studies suggest quercetin may reduce histamine release and inflammation, making it helpful for seasonal allergy symptoms.

Q: Should quercetin be taken with vitamin C?
A: Yes, vitamin C improves quercetin absorption and enhances its antioxidant and anti-inflammatory effects.

Q: Is quercetin safe for long-term use?
A: Quercetin from food or moderate supplements appears safe for most adults, though anyone on medications should check with a doctor trained in natural healthcare.

References:

  1. Antioxidative and prooxidative effects of quercetin on A549 cells. Cell Biol Int. (2007) 31:1245–50
  2. Antioxidant therapy as a potential approach to severe influenza-associated complications. Molecules. (2011) 16:2032–52
  3. The flavonoid, quercetin, differentially regulates Th-1 (IFNgamma) and Th-2 (IL4) cytokine gene expression by normal peripheral blood mononuclear cells. Biochim Biophys Acta. (2002) 1593:29–36
  4. In vivo protective effects of quercetin against sodium fluoride-induced oxidative stress in the hepatic tissue. Food Chem. (2012) 132:931–5
  5. Capasso R, et al. Inhibitory effect of quercetin on rat trachea contractility in vitro. J Pharm Pharmacol. 2009;61(1):115–9
  6. Chang JH, et al. Dietary polyphenols affect MUC5AC expression and ciliary movement in respiratory cells and nasal mucosa. Am J Rhinol Allergy. 2010;24(2):e59–62
  7. Li N, et al. The effect of quercetin on human neutrophil elastase-induced mucin5AC expression in human airway epithelial cells. Int Immunopharmacol. 2012;14(2):195–201
  8. Park H-J, et al. Quercetin regulates Th1/Th2 balance in a murine model of asthma. Int Immunopharmacol. 2009;9(3):261–7.
  9. Rogerio AP, et al. Anti-inflammatory effect of quercetin-loaded microemulsion in the airways allergic inflammatory model in mice. Pharmacol Res. 2010;61(4):288–97.
  10. Nanua S, et al. Quercetin blocks airway epithelial cell chemokine expression. Am J Respir Cell Mol Biol. 2006;35(5):602–10.
  11. Harwood M, et al. A critical review of the data related to the safety of quercetin and lack of evidence of in vivo toxicity, including lack of genotoxic/carcinogenic properties. Food Chem Toxicol. 2007;45(11):2179–205.
  12. Nanua S, et al. Quercetin blocks airway epithelial cell chemokine expression. Am J Respir Cell Mol Biol. 2006;35(5):602–10.
  13. Townsend EA, Emala CW Sr. Quercetin acutely relaxes airway smooth muscle and potentiates β-agonist-induced relaxation via dual phosphodiesterase inhibition of PLCβ and PDE4. Am J Physiol Lung Cell Mol Physiol. 2013;305(5):L396–403.
  14. Impact of quercetin on systemic levels of inflammation: a meta-analysis of randomised controlled human trials Int J Food Sci Nutr. 2020 Mar;71(2):152-163
  15. Int J Sport Nutr Exerc Metab. 2010 Feb;20(1):56-62 The dietary flavonoid quercetin increases VO(2max) and endurance capacity
  16. J Am Coll Nutr. 2017 Jan;36(1):9-15. The Effect of Quercetin on Inflammatory Factors and Clinical Symptoms in Women with Rheumatoid Arthritis: A Double-Blind, Randomized Controlled Trial
  17. Bureau G., Longpre F., Martinoli M.G. Resveratrol and quercetin, two natural polyphenols, reduce apoptotic neuronal cell death induced by neuroinflammation. J. Neurosci. Res. 2008;86:403–410
  18. Penissi A.B., Rudolph M.I., Piezzi R.S. Role of mast cells in gastrointestinal mucosal defense. Biocell. 2003;27:163–172.
  19. The role of quercetin, flavonols and flavones in modulating inflammatory cell function. Inflamm. Allergy Drug Targets. 2010;9:263–285.
  20. Alt Med Rev. 2000;5(3):196-208. Antioxidants and cancer, part 3
  21. Cancer Prev Res (Phila). 2014;7(12):1240-50 Multitarget effects of quercetin in leukemia
  22. Cancer Chemother Pharmacol. 2011;68(5):1161-72. Drug combinations with quercetin: doxorubicin plus quercetin in human breast cancer cells
  23. Pharmacol Res. 2022 Apr;178:106163. Rutin ameliorates inflammation and improves metabolic function: A comprehensive analysis of scientific literature
  24. Crit Rev Food Sci Nutr. 2022;62(3):832-859 The anticancer potential of the dietary polyphenol rutin: Current status, challenges, and perspectives
  25. Oxid Med Cell Longev. 2018 Jun 27;2018:6241017. Rutin as a Potent Antioxidant: Implications for Neurodegenerative Disorders