As someone who has a life-threatening tree nut allergy, I've always been really good about asking about what's in my food before I take a bite. I had a severe reaction after eating cashews as a kid, so when a skin-prick allergy test told me to steer clear of other tree nuts, that's what I did.
Sometimes, though, mistakes happen and a tree nut finds its way into my food — and that can be downright terrifying, as anyone with severe food allergies can understand. But what if someone (and by someone, I mean science) could tell you being diagnosed with a nut allergy doesn't necessarily mean you have it?
It's a phenomenon that I actually have personal experience with, and it's one that University of Michigan researchers recently set out to explain. In a March 2017 study published in Annals of Allergy, Asthma, and Immunology, the researchers looked at data on more than 100 people who had tested positive for a tree nut allergy. All of these people had undergone blood or skin-prick allergy tests in the past eight years — but they hadn't necessarily ingested the nuts to which the tests had found them to be allergic.
The (Risky) Way the Researchers Conducted the Study
In a controlled, doctor-monitored experiment (read: don't try this at home, kids), the participants tried eating small amounts of different nuts while researchers observed their reactions (or lack thereof). Ultimately, the researchers found that a whopping half of the people who had tested positive for a specific nut allergy in the past displayed no allergic reaction when they actually ingested the food. Plus, nearly all of the people with peanut allergies were able to safely eat tree nuts, despite previous tests indicating otherwise.
Take my case as an example: When I ate that handful of cashews as a kid, I found out the hard way that I was very allergic to them. My parents then took me to get a skin-prick allergy test shortly afterward, and my results told me to avoid eating pretty much every other kind of tree nut — but especially walnuts. And yet, when I recently accidentally ingested a walnut (and, of course, went into complete freakout mode), nothing ended up happening.
The researchers think this might happen because some people (such as myself, apparently) have antibodies that react when they receive a blood or skin-prick test... but their bodies don't necessarily show symptoms when they actually eat the food. Who would've thought?
You Should Still Proceed With Caution
Of course, this study was rather small, and more research definitely needs to be conducted to determine exactly what causes the disconnect between blood and skin-prick tests and actual ingestion. But these findings might provide some answers for people who were wondering about their lack of reaction to certain nuts they thought they couldn't eat.
Just remember to consult with your allergist or immunologist before trying any food to which you've tested positive for allergies.