It does have a number of flavinoids to be sure, but it doesn't seem like quercetin is one of them: http://www.ncbi.nlm.nih.gov/pubmed/14733505. But who knows, perhaps these specific flavinoids can also help block mast cell mediators. I haven't looked into them. Histamine is just one of many things released by mast cells. Quercetin is not the only one studied to prove useful for mast cell stabilization, as some Pubmed research will show. Actually, here is the product created by the physician and his team based on their studies: http://algonot.com/product/neuroprotek/. But it's more expensive and has additives that I don't want. But quercetin seems to be the most effective of even these, though much more study would be needed.