Quercetin

Quercetin is a plant flavonoid sold as an "anti-allergy" supplement and promoted for allergic rhinitis to ease a runny nose and sneezing. Convincing benefit for this use has not been shown, and there is no solid evidence base behind it. Allergic rhinitis responds to proven options: intranasal corticosteroids and antihistamines, and in some cases allergen-specific immunotherapy. Do not take quercetin instead of this treatment, or you risk missing care with proven benefit.

ICD-10: J30.9 · ICD-11: CA08.0

Quercetin is a plant flavonoid found in onions, apples and capers, marketed in supplements as an anti-aging and longevity aid, sometimes paired with other so-called senolytics. There is no convincing human evidence that it slows aging, rejuvenates skin or extends lifespan. The compound itself is well tolerated at usual supplement doses. For healthy aging, the approaches that hold up are the proven ones: sleep, physical activity, diet, not smoking and sun protection.

Quercetin is a plant flavonoid found in onions, apples and capers, sold as a supplement for immunity and for preventing colds and respiratory infections. For this use there is no convincing benefit: the data come from small, low-quality trials. For an acute respiratory infection, rest, fluids and symptom relief help, and prevention rests on flu vaccination and hand hygiene. The compound itself is safe at typical dietary and supplement amounts.