Quercetin is a bioflavonoid from fruits and vegetables similar to rutin. Human cell culture studies with quercetin have demonstrated its capability to inhibit the release of histamine from mast cells, a common cause of the symptoms of allergic reactions. It has been shown to be anti-cancer, and inhibit tumour formation. This form of quercetin has been combined with the enzyme Bromelain to facilitate better absorption. The addition of vitamin C increases its effectiveness on the immune system.