Histamine Intolerance vs MCAS: What a Tryptase Test Misses

Colin Renaud described histamine intolerance as a capacity problem. Histamine arrives faster than the body can clear it, largely through what is eaten and how much enzyme capacity is available, and it is not necessarily an immune disease. MCAS, mast cell activation syndrome, is a mast cell behavior problem, where a white blood cell that is part of the immune system releases more than 2,000 chemicals, histamine among them. He added that plenty of people with MCAS have no histamine symptoms at all, because the mediator driving their reaction is something else such as a leukotriene or a prostaglandin. He said the two are not exclusive and can go together, but the mechanisms, the workups and the plans are different.

Dr. Rose said the reaction tracks the histamine load, meaning how much histamine is in a food and how fast the body can break it down. She gave red wine as an example, carrying far more histamine per liter than the point where a threshold is sometimes drawn, and pointed out that more red wine than usual at a party, alongside aged cheese, stacks a lot into one sitting. A very small amount of red wine at home the next week can be completely fine. Clearance depends on enzymes including DAO and HNMT, and medications, alcohol and gut damage all affect how well those enzymes work.

No. Colin Renaud said the older school of thought required an elevated tryptase, and the updated consensus guidelines do not. Dr. Rose added that a tryptase level has to be captured during a flare to mean much, and that hereditary alpha tryptasemia, a genetic condition that raises tryptase, has to be ruled out before an elevated result can be used as criteria. She said the markers worth chasing include heparin, histamine, N-methylhistamine and prostaglandins, and that the testing is temperature sensitive when the blood or urine is drawn. It is run at specialty clinics, only a handful in the country that he knows of, and he said he does not have that capability himself. In her own practice, she said, the assessment is largely clinical.

Dr. Rose said her understanding is that the figure traces back to a paper written in 2013, built on a self-reported symptom questionnaire where the authors themselves listed self-declared diagnosis as a limitation. Her short answer was that 17 percent is probably much higher than reality. Colin Renaud disagreed. He said the older standard that required an elevated tryptase misses a large group of people, and that the newer consensus criteria give much better updated guidelines. He put it down to criteria: whether a diagnosis rested on objective data or on symptoms and response to treatment, and he said the percentages are extremely hard to hone in on because the workup differs from clinician to clinician.

Dr. Rose said a list that keeps narrowing means the plan needs to change. She uses a low histamine diet as a short term tool and as part of the diagnostic process, with the goal of widening the diet back out again, and a list that keeps shrinking starts to worry her about nutrient status and immune health. Colin Renaud said this is where testing actually begins, because something is driving the worsening, whether that is gut health, an infection, mold exposure, a hormone problem or a nutritional imbalance.

Dr. Rose answered a viewer who developed hives during her cycle by framing it as a threshold problem. She said hormones and hormone fluctuations can often play quite a role in histamine tolerance, and she would not say that being premenstrual creates the histamine intolerance. She added that they see a woman's symptoms fluctuate with the part of the month she is in all the time in clinic.