Food Allergy Nature versus Nurture

I honestly didn’t think I would be blogging about the science of food allergies this often, but the articles keep coming!  This article is about a study by a prominent food allergy researcher, Dr. Kari Nadeau, and involves newer, more revealing food allergy blood tests:

There can be arguments in the food allergy community over how reliable current food allergy blood testing is, but there’s no doubt that it is far from 100% accurate.  Most allergists recommend skin testing as more accurate, that that still falls short of being fool-proof.  From the article:

“The IgE blood test only represents a protein which is 1/100th of all the items we think are involved in allergy,” explains Dr. Kari Nadeau…“IgE is important, but it is not the only marker.” A high level of IgE can indicate an allergy, but it may not; and some severely allergic people have low IgE scores.

Clearly, something more accurate would be nice.  The “gold standard” is still considered by many to be the oral food challenge–particularly if the food has never been ingested, or the triggers haven’t been clearly identified.  Performed in a specialty room of an allergist’s office, an oral food challenge involves eating a potentially problematic food (often in increments) in order to see if the person reacts.  If they do, trained personnel have all necessary drugs on hand, so response is swift and complications are generally minimal.

I insisted on peanut challenges for both of my sons, because through various circumstances both of them were skin tested (and were positive) for peanut before they’d ever so much as sniffed an open jar of peanut butter.  Both challenges revealed that they boys did have allergies.  I was disappointed, but felt more confident knowing for sure that they were allergic.  In my opinion, strict, life-altering food-avoidance routines are totally not worth it if the child isn’t actually allergic to peanut (or whatever food.)

A lot of parents don’t share my views on this, however, or even if they do, they encounter obstacles that stop them before they reach a food challenge.  Allergist resistance and fear of what might happen can stay the hand of many who might otherwise admit that a food challenge would be a wise choice. The new blood test Dr. Nadeau is developing might give more accurate results without the stress of a food challenge:

Nadeau (in collaboration with …[others]…) has recently patented a new diagnostic test that could be easily done with a few drops of blood from the heel stick of a newborn. 

The diagnostic allergy test (DAT) involves mixing the blood with 90 different potential allergens…to measure the reactions in various types of white blood cells. …Pilot studies so far suggest that they can identify allergies with 95 percent accuracy.

95%, that’s pretty darn accurate.  Nearly everybody I know who deals with food allergies would like something like this.  But one little detail makes me wary–this being done from the heel stick of newborns.

Don’t get me wrong, every time I read an account by newly-diagnosed allergy parents who watched in horror while their child swelled up like a hivey, red balloon and barely made it to the hospital, I agree that it would be nice to be able to predict and prevent this.  Nobody wants that to happen to a child, and most parents aren’t expecting any such reaction and are totally unprepared.

However, this makes it sound like a person is either predestined to have allergies or is not.  And that seems unlikely.  Nearly every science article I’ve read involves identifying factors that increase or decrease chances of developing food allergies.  And Dr. Nadeau herself is known for her oral immunotherapy studies, in which she aims to change people’s reactions to allergenic foods.  How does this blood test relate to the arsenal of environmental factors that a baby comes into contact with after leaving the hospital?

In fact, since “food allergies require an exposure to the food in order for the immune system to mount a response,” I find it hard to believe that most newborns can be allergic to much of anything.  Unless food proteins are able to cross the placental barrier, newborns generally can’t be allergic to a food until they’re exposed to it, whether through ingestion, in mother’s breast milk, or sometimes through skin contact.

That makes me wonder what adding heel-stick allergy tests would mean to most newborns.  The test, so far, is showing 95% accuracy, but if performed on a large chunk of the population, would that number hold?  Would an increasing number of families adopt strict food-avoidance routines simply because a test told them so, only to realize years later that their child either quickly outgrew the allergy, or it never existed in the first place?

Conversely, would parents disregard symptoms of food allergies as something else, because the newborn heel-stick test told them their child didn’t have any allergies?  In this way they might miss an initial, minor reaction and only catch it when it progresses to something much worse.  Heck, that happens to enough parents just because they aren’t familiar with food allergies!

Clearly, I don’t know enough about this.  I’ll be curious to hear about further advances in this test, and maybe get some questions answered along the way.

And as if this blog post wasn’t enough like a term paper, there’s still more to discuss.  Dr. Nadeau has also developed another blood test aimed at predicting the severity of food allergies:

Nadeau has developed another new blood test called the therapeutic exam for allergy (TEA) that examines genes that play a role in the allergic response. One such gene, called FOXP3, is found in a type of white blood cell whose job it is to modulate and suppress other cells that are becoming inflamed or overactive, as happens in the case of an allergic reaction.

Nadeau has discovered that in food-allergic individuals this gene is disabled by a chemical coating that prevents it from being expressed (a change not in the genetic code itself, but in the way the gene functions, known as an epigenetic change).

People who have been diagnosed also often wish they could be told how severe their (or their children’s) allergies will be, but unfortunately, that usually isn’t possible.  Countless times, someone who only reacted with mild hives the first time around goes into full-blown anaphylaxis the second or third time they’re exposed to a food.  There’s been no way to predict whether this will happen, or if the extent of the reactions will always remain at hives.  Strict avoidance is the order of the day for the vast majority of food allergy families.

This test seems like it could be very useful, indeed.  If there are actually markers in the body that would indicate whether or not a person will progress to anaphylaxis, knowing that would bring peace of mind to a good many families.

I’ll be eagerly awaiting more information on this test as well.


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