Quercetin is a natural flavonoid found in many fruits, vegetables, and grains. It is particularly abundant in foods like apples, onions, and berries. Known for its antioxidant properties, quercetin helps protect cells from damage caused by free radicals, which are unstable molecules that can contribute to various diseases. Research suggests that quercetin may have anti-inflammatory effects and could support immune function. Some studies indicate it might help reduce allergy symptoms and improve heart health. However, more research is needed to fully understand its benefits and potential uses in health and nutrition.