My six-year-old son is anaphylactic to peanuts. This we know with certainty because, after eating two bites of a PB&J when he was two years old, he experienced a swollen tongue and lips, congestion, runny/itchy/red eyes, vomiting, and head-to-toe hives.
My daughter was just six months old when my son had his anaphylactic reaction to peanuts, and the day after his reaction we became a peanut-free house and have been that way ever since. And with an older sibling who has a severe food allergy, the typical advice at that time was for the younger sibling to avoid that allergen until age 5. (New recommendations can be found here.) Thus, my daughter was never given a taste of peanuts.
Two years ago as we prepared to take a trip to an all-inclusive family resort, I began wondering whether my daughter also had a peanut allergy and whether we should be carrying an EpiPen for her. The resort where we were going to vacation operated like a day camp for the kids. That is, the kids spend much of the day away from their parents in peer groups, and eat all three meals away from their parents. I felt the need to know whether my daughter also needed an EpiPen, especially since she’s shy and would be eating meals away from me and not prepared by me.
So we visited the allergist for a skin prick test and were a bit dismayed to learn that the results were positive for a peanut allergy. But, all in all, the news wasn’t devastating like it was with my son since we were already comfortable carrying epinephrine and living peanut-free.
Choosing a Peanut Component Test
Last summer when there was so much talk about peanut component testing in the allergy community, I figured this test would be perfect for my four-year-old daughter: she had never been exposed to peanuts but had a positive skin test and had been avoiding. What a great opportunity to find out for sure whether she was truly allergic. Or so I thought.
After calling around, I found an allergist in our area who would do component testing. When we went for the appointment I didn’t realize there were two different component tests since I’d heard about only the UKnow test. The allergist explained that the ImmunoCAP component test would test for a whole host of allergens, such as tree nuts, which my daughter also had never eaten, and that the UKnow* test, though it was a more sensitive component test, would test for only peanut. The price for the two tests was similar, and because both are expensive, we had to choose between the more comprehensive food allergy test or the more sensitive peanut only test. We opted for the ImmunoCAP test.
When the results came in, the allergist interpreted them to mean that my daughter did not have a peanut allergy. The only thing, in fact, that she tested positive for was cats. The allergist’s proposed next steps were to redo the skin prick test and if the results were negative, which she believed they would be, we could do a peanut challenge at home (!). I was completely averse to doing a peanut challenge at home and didn’t want to deal with this allergist’s overly busy office for yet more appointments, so we found a new allergist.
Our new allergist came highly recommended. I took all of my daughter’s test results to the appointment, and was surprised to learn that he doesn’t even do component testing because, according to him, the results can be difficult to interpret. I had asked the first allergist about this: because my daughter has never been exposed to peanuts, could she have the IgE antibody for peanut allergy but at such low levels that they are undetectable by the test? The first allergist seemed to think this line of thinking was completely incorrect; however, our new allergist agreed that this was exactly why he doesn’t do component testing. He eagerly flipped through the component testing results since he’d never seen component test results before.
After taking her history and reviewing all the test results, our new allergist recommended an in-office peanut challenge so we would know once and for all whether our daughter was peanut allergic.
I’ll skip ahead and let you know that my daughter did not pass the oral food challenge, though her reaction was much delayed.
First, never do an in-home food challenge if your child or anyone in your family has a history of food allergies. If your family doesn’t have a history of food allergies but you’re uncomfortable doing a food challenge at home and your allergist refuses do one in the office, find a new allergist.
Second, if your child has never been exposed to peanut before, no test other than a food challenge will give you a definite answer as to whether your child is peanut allergic. My daughter passed the ImmunoCAP component test but failed the food challenge for peanut; the test was not sensitive enough to detect her IgE antibodies for peanut.
Of course I’m left wondering two things: 1) Would the UKnow peanut component test have accurately predicted the presence of peanut allergy had we opted for the more sensitive but less comprehensive testing? And 2) What do her IgE blood levels look like now? I’ll never know the answer to number 1 since she has now been exposed to peanut and her body has probably produced more IgE antibodies as a result. Because the ImmunoCAP test was inaccurate in predicting the presence of peanut allergy, I have zero confidence in the results of any of the other food or environmental allergens it tested – what a waste of money. (We already knew she had a cat allergy, which it accurately predicted, but she had been exposed to cats many times.)
As for #2, because I feel like I’ve put her through enough testing for one year, I won’t know her blood levels until we go back for retesting and, if we’re diligent and lucky, we’ll never know her blood levels immediately after exposure. Because her reaction was mild – which I’ll detail in tomorrow’s post – I’ll consider requesting the UKnow test the next time we go for blood work if sufficient evidence of the test’s reliability exists.
Tomorrow, I’ll post about her food challenge in case your child has never gone through one and you’re curious about how it works.
*Update April 2016: I can no longer find information on the uKnow component testing. Presumably it was discontinued or renamed. If I find out what happened to it, I’ll post another update!