New Peanut Allergy Blood Test

Guys. There’s a new blood test for an allergy to peanuts that is way better at actually predicting severe peanut allergies that skin or IgE blood tests (remember, those have around a 50% (!!!!) false positive rate). But before we get into how the new blood test works, we gotta remember how food allergies and the current blood test works.

First off, food allergies are immune system mediated, unlike food intolerances or sensitivities (which deal with your GI system). For food allergies, your immune system recognizes the food with antibodies (specifically immunogloblin E, or "IgE") that trigger a reaction which can include runny nose, hives, difficulty breathing, nausea, continuous vomiting, lightheadedness… You know, your normal anaphylaxis stuff. Antibodies are super important for our immune system to recognize and fight off viruses and bacteria and we have all kinds that are constantly floating around in our body. But, they are not useful when they cause our body to react to foods that should be perfectly safe for us to eat.

Allergen binds to IgE, blah blah blah science/magic blah blah --> anaphylaxis

You're welcome, I was a biology major.

The normal IgE blood tests measure how much allergen-specific IgE antibodies are in a person’s blood. Does it give us any information about the predicting the severity of a reaction? Nope. Is it a great test to use on its own? Definitely not. That’s why an oral food challenge is still the gold standard for food allergy testing.

So, what’s different about this new test? Well, it turns out that there are a lot of different sites on a peanut protein where antibodies can bind. Out of the 64 possible binding sites, one study found that a specific site- Ara H 2 is a much better predictor than general peanut IgE. Allergenis, a company who is offering this new "epitope mapping test" that looks at the different binding sites on the peanut protein has even divided positive results into 3 different levels which predict how much peanut you can eat before having a reaction.

To me, this is huge. My kid has only had a very small amount of peanut butter one time and then had a very mild reaction. But, she’s needed epinephrine for milk and egg. So do we need to be more worried about milk and egg because that's what she's had a big reaction to? Or should we be more worried about peanuts because that's what everybody thinks of when they think of severe food allergies? Do we need to avoid anything that’s been processed next to peanuts? What about eating next to a sticky fingered friend chowing down on a peanut butter sandwich?

We have been totally, strictly avoiding peanuts for over 2 years now. It’s made it hard to find tree nuts that she should be safe to eat because tree nuts are often processed right next to peanuts. It’s made me nervous pretty much whenever we are in public, surrounded by ubiquitous peanut butter and jelly sandwiches, packs of nabs, and Reeses. 

So, if it seems likely she could handle 1/3 of a peanut and we can be 25% less crazy about food allergies? What a relief! And if it turns out she’s extremely allergic (ugh, please, no) at least we will know we are validated in being insane people around peanuts.

PS: WHY ARE PEANUTS EVERYWHERE? I’M LOOKING AT YOU, HALLOWEEN.