Food allergies have become extremely common in our collective daily experiences. I recently got my turn to buy snacks for my daughter’s kindergarten class and was impressed by the lengthy allergy list, as I kept glancing at it furtively for compliance while I raced through the snack aisle at the store.
8% of US children are currently affected by food allergies and recent epidemiologic trends reveal a progressive rise. In keeping with this quasi rule of 8’s, largely just 8 food groups cause this rather impressive prevalence of food allergies. These are milk, egg, peanut, tree nuts, wheat, soy, fish and shellfish. There has always been a hasty approach by parents to designating children as having food allergies. We need to remember that allergy have a very specific immune mechanism and that not all adverse food events are truly allergic. Some are more appropriately food intolerances. The distinction is important because it’ll help our understanding of the intriguing world of immunology and how diagnostic testing for immune mediated (allergy) diseases however enchanting can fall short of correctly identifying true allergies. The quality of life issues and fall out that follow an incorrect food allergy designation can last a lifetime and affect socialization and frankly gustatory delights that’ll make the Travel Channel’s, Anthony Bourdain jealous.
How are food allergies diagnosed?
The medical history is very important and providing your healthcare provider with a good run of events preceding and surrounding the sentinel allergy event is a great start. We encourage the use of a diary and conscientious documentation of food items ingested. The importance of this chronicle of foods eaten, was it cooked? baked or eaten raw? and reactions observed cannot be overstated. How soon after exposure did the symptoms occur? What symptoms were observed? Because often, the careful identification and informed elimination of the likely culprit(s) may be all that’s necessary. Diagnoses of food allergies or intolerance can be made this way and when done appropriately fall into the very high pedigree of statistical accuracy called “ a trial of 1”. Specific blood testing looking for presence of antibodies to food allergens by measuring the levels of the antibody most commonly associated with allergies, called IgE are common in everyday clinical practice. When this is combined with a skin-prick test, the diagnostic accuracy improves. It would be fine if the immune system were as simplistic as that. A system that’s so uniquely adapted and continually evolving to memorize every invader that’s ever breached its defenses and program itself to make antibodies or get cells battle ready to stop that invader or others related to it next time they get lucky enough to get inside while maintaining surveillance for cancer cells and preventing the body from turning its own more than a billion troop of soldiers on itself surely would be more complicated. It is! There are food allergy mechanisms that by-pass the process above, termed non- IgE mediated or use some combination of it with other mechanisms. Blood or skin-prick testing would not readily detect these. It is also possible to find a positive test as described above to food a child is eating presently without any difficulty. This is where a careful patient exposure and observed reaction history is truly worth its weight in gold. This eliminates indiscriminate testing and optimizes the physician’s chances of correctly making the food allergy diagnosis.
To be continued next week…