February 22, 2019
by Russell Johnston
“True allergy.” The phrase seems to be in flux right now. Some doctors and allergists are still using it to mean exclusively IgE reactions, apparently unaware that non-IgE Mast Cell Activation Syndrome [MCAS] (and even non-histamine reactions) can kill; which is clear in the literature. So that’s a very dangerous way of using the phrase. It can lead to situations as shown in the above photo, where patients are in hospital with anaphylaxis reactions to food… but magically - according to some medical professionals - they don’t have “real allergies” even though they might have real funerals from their reactions.
Here’s an interesting example from a medical journal article that dances around the phrase, from 2015:
“An estimated one-fifth of the population believe that they have adverse reactions to food. Estimates of true IgE-mediated food allergy vary, but in some countries it may be as prevalent as 4–7% of preschool children.”
The authors didn’t quite use the magic phrase “true allergy”, but as the text of the abstract goes on, they leave themselves very little wiggle room either, and no room the existence of MCAS. So again, many histamine and innate immune reactions that kill just as IgE reactions do, magically aren’t going to be “allergies” according to the authors.
Others are using “true allergy” a bit more broadly, to mean any reaction that can cause life-threatening anaphylaxis. But they are assuming that such severe reactions are almost certain to be IgE reactions (not so clear, and not for some patients), or assuming that anaphylaxis kills by closing the throat and obstructing breathing (just one way it can kill), or assuming that patients are very good at telling when they’re in big trouble (very dubious, even doctors often miss or don’t ask about heart symptoms from angioedema), or just as a way to shut down the conversation.
Not infrequently the medical professionals using the phrase “true allergy” either don’t believe MCAS exists, believe it is very rare (false) or just haven’t heard of it. It’s not rare for doctors to be behind the times, that’s how the system is set up (certainly where I am): GPs aren’t paid to read. So some don’t, or don’t much — after all, they hardly have time to keep up with insane patient loads, because governments don’t want to pay to educate enough doctors. Even Specialists often restrict their reading to journals of research-highlights, journals that often play it safe about what research they highlight and avoid controversy.
Of course, it’s true and annoying that a great many people use the word “allergy” to mean all sorts of things: relatively small food reactions that may not involve the innate immune system or mast cells at all, for example. I can’t blame medical professionals for trying to push back on that, but if they do that by implying or flatly stating that there’s a clear, easily understandable or litmus-testable line between allergies-that-kill and reactions-that-are-trivial they’ve gone well overboard. Bodies (and brains, which do mix into innate immune system reactions) are very complex, and it’s just not that clear. MCAS isn’t that clear-cut — it’s extremely protean (shape-shifting.)
In all honesty, there is no medical definition (or medically useful definition) for “true allergy” today — if only because the same non-IgE reaction that is bothersome but hasn’t yet caused life-threatening anaphylaxis previously, might be life-threatening tomorrow. Yet we’re talking about the same reaction happening according to the same mechanism in the same patient. If medical professionals were willing to call MCAS reactions “true allergies” and then say that some “true allergies are not yet life-threatening in a given patient,” that might be useful. But as I said a couple paragraphs above, right now the motivations of those using the term are generally opposed to any such statement, and they often don’t acknowledge the existence of MCAS at all.
I hate to say it, but my experience so far has been that when a researcher or specialist uses the phrase “true allergy,” they’re probably signalling that they haven’t read much recent literature, or have read too narrowly, and may be putting patients at risk. I hope that changes, but there’s still plenty of ignorance to go ‘round about MCAS right now, inside and outside of the medical professional — not too surprising since it’s only recently been recognized.
The risks are real. I’ve corresponded with a mother who lost her daughter to a mast cell reaction. Because the daughter didn’t respond to antihistamines, the hospital declared the death to be a very rare reaction to Benadryl, with no evidence of such an IgE reaction in the case, and despite the fact that the patient previously well-tolerated by the patient Benadryl, which had been given after the reaction had become severe. The hospital couldn’t bring themselves to imagine an allergic reaction that wasn’t histamine-mediated. They didn’t alter their procedures.
For a glance at that recent history of MCAS, click here:
MCAS (Mast Cell Activation Syndrome) — Is that a real disease? (citations)
Previous article in this series:
Understanding why MCAS (Mast Cell Activation Syndrome) triggers do what they do:
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