Doctors Best Quercetin Bromelain is a potent antioxidant formula to help support histamine balance within the body, perfect to support the body's response to allergens. Quercetin is a bioflavonoid from vegetables and fruits, that may support both the cardiovascular and respiratory system. Bromelain is a proteolytic enzyme derived from pineapple, it supports tissue comfort and may support quercetin absorption. Bromelain also has also shown to support the breaking down of fibrin, to support tissue healing.