By Henry Ehrlich
I once heard the writer and movie director Nora Ephron (now, sadly, no longer with us) use a term on a late-night talk show that has defined a category of knowledge for me ever since. The term was “dynamite fact.” Dynamite facts are items that are interesting in and of themselves, and might or might not connect to some larger point. One of the reasons I enjoy writing about allergies is that I continually encounter dynamite facts and upon reflection occasionally fit them into a bigger picture.
Many food allergy parents are acquainted with component testing, the ThermoFisher technology that measures reactivity not to the whole food but to epitopes—components—of the allergenic proteins. The best known of these is the “uknowpeanut” test, which measures reactivity to five components: Ara h1, 2, and 3, which place the patient at high risk of anaphylaxis; Ara h8, which is associated with mild reactions in and around the mouth; and Ara h9. Ara h8 is also similar to the allergenic component Bet v 1 in birch pollen, which can cause nasal allergies, and to allergens in fresh fruit that cause reactions comprising oral allergy syndrome (OAS). (Ara h9 seems to have strong relevance for Mediterranean people for whom 1,2, and 3 are less important.)
Like most other amateurs, and some professionals, I committed these facts—unlike dynamite facts, ordinary facts are meaningful but not on their face always that interesting–to memory, but without any understanding of the distinctions that would reveal a bigger context. This morning, however, while researching a problem posed in a Facebook group, I happened to revisit Scott Sicherer’s new book Food Allergies, which I recently reviewed, and came across the dynamite fact that what distinguishes the relative safety of the Ara h8 epitope from 1,2, and 3 is that it is easily digested, whereas the lower numbers are harder to digest and survive all the enzymes and acids that break down foods so their nutrients can be utilized. Light-bulb moment. If Ara h8 is pollen like, then it stands to reason it would react with tissues that react with pollens and, like pollens, go no further, while those other rugged components survive to raise havoc. It also might explain the variability in reactions. Depending on the state of the digestive system and the size of the dose, the allergic response might be more or less serious. It also puts into perspective the state of the gut microbial environment, since microbes also play a part in digestion.
Diagram by cuerpo-sdigestivo.blogspot.com