Benefits / uses
Allergies, Asthma, Hay Fever and Hives
In test tubes, quercetin prevents immune cells from releasing histamines, chemicals that cause allergic reactions. On that basis, researchers think quercetin helps reduce symptoms of allergies, including runny nose, watery eyes, hives, and swelling of the face and lips.

Heart Disease
Studies suggest that the flavonoids quercetin, resveratrol, and catechins (all found in high concentration in red wine) may help reduce the risk of atherosclerosis (plaque build up in arteries that can lead to heart attack or stroke). These nutrients appear to protect against the damage caused by LDL ("bad") cholesterol and may help prevent death from heart disease. However, most human studies have looked at flavonoids in the diet, not as supplements.

High Cholesterol
Test tubes studies show that quercetin prevents damage to LDL cholesterol, and population studies show that people who eat diets high in flavonoids have lower cholesterol. One study found that people who took quercetin and an alcohol-free red wine extract (which contains quercetin) had less damage to LDL cholesterol.

Hypertension
Studies show that quercetin supplementation reduces blood pressure in people who have hypertension.

Interstitial Cystitis
Two small studies suggested that people with interstitial cystitis might benefit from flavonoids. People with this condition have bladder pain, similar to a bladder infection, and often experience an urgent need to urinate. In both studies, those who took a supplement containing quercetin appeared to have fewer symptoms.

Prostatitis
Some preliminary evidence indicates that quercetin might reduce symptoms of prostatitis (inflammation of the prostate). One small study found that men who took quercetin had a reduction in symptoms compared to men who took placebo.

Rheumatoid Arthritis (RA)
There are reports of people with RA who had fewer symptoms when they switched from a typical Western diet to a vegan diet with lots of uncooked berries, fruits, vegetables, nuts, roots, seeds, and sprouts containing antioxidants, including quercetin..

Cancer
Quercetin and other flavonoids contained in fruits and vegetables. Scientists have long considered important in cancer prevention. People who eat more fruits and vegetables tend to have lower risk of some types of cancer. And animal and test-tube studies suggest that flavonoids do indeed have anti-cancer properties. Quercetin and other flavonoids have been shown in these studies to inhibit the growth of cancer cells from breast, colon, prostate, ovarian, endometrial, and lung tumors.

Doses
Recommended adult dosages of quercetin vary depending on the condition being treated. The following are guidelines: