Quercetin is a very potent bioflavonoid found in red wine, green tea, tomatoes, onions, and green beans. It is a natural anti-oxidant, which protects cells in the body from damage by "free radicals". Heart disease and high cholesterol is partially caused by free radical damage to blood vessels. It may protect against heart attacks and strokes. It is recommended as a treatment for allergies, hay fever, and asthma because it helps prevent immune cells from releasing histamine, the chemical that initiates the itching and sneezing. It can reduce swelling of an allergic reaction; helps prevent itchy eyes, runny noses, and scratchy throats. Quercetin in animal studies has shown to protect against a variety of cancers; may help stop cancer at its earliest stage by preventing the damaging changes in the cells that initiate cancer.