Food Allergy Testing

 

Having a food allergy is pretty bad, but the testing process might actually be worse. If you think you’ve had an allergic reaction to a food, it’s not always easy to pinpoint what exactly was the cause. Starting solid foods with your kid can be a stressful process no matter what, but it’s exponentially more stressful when you don’t know what is going to be safe to eat. And because the only way to truly test for a food allergy is to eat the food and see if you have a reaction, there’s a lot of guess work in the diagnosis process. The oral food challenge is the gold standard in food allergy testing.

Oral Food Challenge

It sounds exactly like what it is. You give the person the food you think they are allergic to and see what happens. But because if the test is positive, you’ve purposely induced a severe allergic reaction, they’ve made up some standards to make it safer.

You only do it at the doctor’s office.

They start by giving you a very small amount of the allergen, then waiting for a reaction. If there’s no sign of a reaction, more food is given.

If there’s no reaction by the end of the challenge you aren’t allergic! Yay! But if there’s any sign of a reaction, the test is stopped and you are given medication and monitored at the office. It takes 2-4 hours (that’s right HOURS) so go ahead and mark out the rest of the day. And bring toys. And books. And a stroller. And you know what? Just be a crazy person and move right on in to that room and make yourself comfortable.

We’ve been through 2 oral challenges. One (soy) with no reaction- it was so fun! My kid now loves soy yogurt and soy milk and tofu and it opened up a lot of foods for her to eat. She got soy yogurt all over her face and had a huge smile the whole time. Would highly recommend.

The other one (baked egg in a muffin) was stopped early and she eventually needed epinephrine. Not fun.  Not only did she have a severe allergic reaction at the doctor’s office, afterwards she was 1) scared of all doctors and cried bloody murder even when just getting weighed and 2) refused to eat baked goods including her birthday cupcakes that I had lovingly made for her. Months later, she’ll eat a vegan muffin. She is still not sure about any medical office.

Skin Test

Because the risk of food challenges going not great (I mean really, inducing anaphylaxis just doesn’t seem like the best idea), doctors usually first try alternative testing that doesn’t give a definitive diagnosis but can give them more information. Usually, this means a skin prick test.

You go to the doctor, they scratch your skin with a little bit of the suspected food, wait 20 minutes, and see if you have a reaction. They are looking for a wheal to appear and will measure the raised bump portion and the surrounding red circle.

Good things? You get the test results immediately and it really doesn’t take that long. Ok, so trying to keep a baby happy for 20 minutes when you have to hold them a certain way so you don’t touch anywhere they’ve scratched the skin (her entire back) was an upper level parenting challenge. But it was one I excelled at, especially by the third time.

Also good? They are also extremely sensitive. This means that if you are allergic to the food, you will get a positive result. So, if you are going to the doctor for a skin prick test, and you don’t have a reaction (or a big enough reaction compared to the controls), >95% of the time you can eat that food without fear of allergies.

Unfortunately, they are not specific. About half of the time you get false positives, which means that if you get a positive result, you have a 50% chance of not actually being allergic. You could completely change you diet, avoid a certain food, and then it be all for nothing. That’s a big old bummer.

My kid has had 3 rounds of skin testing. The first round happened after her initial reaction to peanuts. It was a pretty mild reaction, but we got referred to the allergist and this was the first thing she did. They ended up testing a lot of the top 8 and other common allergens and she tested positive to both peanuts and eggs. She already had the reaction to peanuts when she ate them so that coupled with the skin test made it pretty clear that she’s actually allergic. Eggs, we had to avoid until she could safely try them in the office during a food challenge.

Then, she had a full blown anaphylaxic reaction and we didn’t know what she had reacted to. Round 2 of skin tests came back positive for garlic. At this point, I felt like going to see the allergist was the worst. Every time we went, we get another thing she’s allergic to that we have to avoid! I thought being allergic to peanuts was terrible. Then I realized how much stuff eggs were in. Now garlic?! Garlic is in every premade sauce, salsa, curry, spice mix, prepared food in the entire universe. She didn’t actually have any garlic on her plate, but the rest of the family was eating it. Maybe it somehow contaminated her plate? Now, keep in mind, there’s a 50% chance she’s not actually allergic to garlic. But that was just our best guess for the cause.

About 1 month later, she had another round of anaphylaxis, this time no garlic in sight. No peanuts in sight. No eggs in sight. It was the first time she was eating cheese. And you know what she was eating last anaphylaxis? Yogurt. It’s got to be milk, right? Even with the negative skin test? So round 3 of skin tests, here we go.

Milk. Still negative.

Our NP doesn’t believe it and repeats the test the same day. There’s a little bit of a wheal but nothing like the other positive skin tests.

Now I have lost all faith in these results. If she can have a false negative to milk and still have full blown anaphylaxis including trouble breathing and repetitive vomiting then how can we trust any of the other negative skin tests? That’s the one thing they are supposed to be good for! Not trusting all of the negative results meant that we did most of our new food trying during weekend lunch when we had two parents home and time for a 4 hour trip to the ED if the worst happened.

 

This 3 month period between her having her first reaction to peanut butter to feeling more confident of her full allergy list has been the worst part of having a kid with food allergies. Avoiding foods is hard work, but the first step is finding out WHICH foods to avoid. So, if you are going through this stage now, know that it does get better. You get used to looking at food labels. You get used to checking twenty times to make sure you have two non-expired epinephrine auto-injectors whenever you leave the house. And eventually, you find out what is safe (and what is not safe) for your kid to eat.