Dr. Amy Nett: With histamine intolerance, there are a few different potential causes of the histamine intolerance. It might be that there are very high levels of histamine or it could be that histamine isn’t being broken down, so it’s difficult to know where to start in terms of supplementation, whether you want to start with DAO or if you want to start with bromelain and quercetin. We use a product called Quercenase from Thorne, and that contains both quercetin and bromelain, so I might say Quercenase instead of specifically saying both of those. What we often do is start patients with both diamine oxidase and Quercenase because they are treating these symptoms from different approaches. The diamine oxidase is breaking down the histamine that is already there, whereas quercetin and other antihistamines actually reduce the amount of histamine produced, so patients may respond better to one over the other depending on the nature of their problem.
There is a test through Dunwoody Labs that can actually test the levels of DAO and histamine, so that may give you some indication, but clinically I generally don’t find that as helpful because for much less money, you can give patients these supplements, see how they respond, and that’s often your best guide. Absolutely have them on a Paleo, low-histamine diet, and then you can try both DAO and Quercenase. As they improve, they can try taking out one or the other, and again, hopefully you’re addressing the underlying issue while they’re taking these supplements so that they can eventually wean off them and have a more normal histamine tolerance.
In terms of the causative factors of histamine intolerance, of course, SIBO is one factor. Then the question if SIBO is not a causative factor is, what else do you consider? Definitely think about dysbiosis or any other cause of leaky gut. Maybe they’re eating foods that are triggering them and that’s causing leaky gut. Dysbiosis from an imbalance of the good and the sort of more pathogenic microorganisms—yeast overgrowth, parasites—those all might contribute to histamine intolerance.
The other thing I do actually think of is chronic inflammatory response syndrome, also known as biotoxin-related illness. Personally some of the most severe cases of histamine intolerance I’ve seen are actually associated with chronic inflammatory response syndrome, so I would include that in my differential, especially if the patient is on a low-histamine diet and they haven’t responded at all to the Quercenase or the DAO supplementation.