This Test Can Determine Whether You've Outgrown A Food Allergy : The Salt Food allergies are tricky to diagnose, and many kids can outgrow them, too. A test called an oral food challenge is the gold standard to rule out an allergy. It's performed under medical supervision.

This Test Can Determine Whether You've Outgrown A Food Allergy

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Now an estimated 4 percent of Americans have food allergies, and that can show up very early in life. But many kids actually outgrow some of their allergies. NPR's Allison Aubrey reports on a surprisingly simple test that can tell if they have.

ALLISON AUBREY, BYLINE: Signs that a kid may be vulnerable to food allergies can show up in infancy. Kendall Cieciuch, who lives in Telluride, Colo., says she remembers exactly when she saw it in her daughter, Jula.

KENDALL CIECIUCH: When she was a baby, really 5 months old only, she had really bad eczema.

AUBREY: And by the time Jula was a toddler, allergists had diagnosed her with a bunch of food allergies.

CIECIUCH: The main groups were dairy, eggs and nuts, and tree nuts being the worst of those.

AUBREY: Jula, who is now in fifth grade, had to avoid all of these foods for years. A few accidental exposures did cause reactions so her mom says she had to be super vigilant.

CIECIUCH: It definitely restricted her, and I would prepare food everywhere we went. Then last summer, the Cieciuch's got some good news. Jula's allergy doctors at National Jewish Health in Denver had redone her blood tests, and the new results suggested that she may have outgrown some of her allergies. The blood test measures the levels of a certain type of antibody. The higher the level, the more likely a person is to have an allergic reaction. Jula's blood revealed a drop in the antibody, but the only way to confirm that it was safe for Jula to eat a food she'd been allergic to was to take another test. Doctors call it an oral food challenge. Basically it means you try to eat small quantities of the foods you've had to avoid. Here's Jula explaining the test, which is done under a doctor's care.

JULA: What they do is, they give you a really, really small dose, like, a crumb, basically.

AUBREY: For Jula, it was a crumb of egg. Then after 20 minutes, if you don't have any reaction...

JULA: Then you can take a dose that's a little bit bigger.

AUBREY: If you worked your way all the way up to a whole egg, you've passed, which means you're no longer allergic. The day Jula passed her egg challenge...

JULA: I was so glad and happy because for so long it'd be, you can't eat this, you can't eat this. And then I could eat it. I was very emotional.

AUBREY: In addition to egg, Jula can now also eat walnuts and almonds. She's still allergic to some foods including cashews and dairy, but her mom says adding so much back to her diet makes life easier.

CIECIUCH: It's a huge relief. It's - it really opened up her diet a lot.

AUBREY: Jula's story is not unusual. An estimated 70 percent to 80 percent of kids outgrow egg allergies. Now a new study sheds more light on just how many people have come to find out they can eat foods they've long avoided. Researchers studied the results of about 6,000 oral food challenges all done in adults and children who doctors suspected had become tolerant to foods they'd once reacted to. What they found is that only 14 percent of those patients had an allergic reaction during the test. Two percent had serious reactions. But the vast majority, 86 percent, did not have an allergic reaction at all.

B J LANSER: From a big-picture standpoint, I think it is very encouraging.

AUBREY: That's B.J. Lanser. He's a pediatric allergist at National Jewish Health in Denver. He was not involved in the study, but he says the findings mirror what he sees in practice.

LANSER: It's possible that these children in the study have outgrown their allergy.

AUBREY: Just like Jula did. Or, Lanser says...

LANSER: It's also possible they've never truly had a food allergy.

AUBREY: He says it's tricky to diagnose food allergies. That's because the two main tests doctors use, the blood test and the skin-prick test, only reveal part of the story.

LANSER: Both tests only measure sensitization. They can't tell you or diagnose you with a food allergy. They can't tell you about severity. All they can tell us is how likely you are to react when you eat the food.

AUBREY: And that's where the oral food challenge comes in. It's become the gold-standard test to rule out an allergy. So if you or your child tested positive for a food allergy years ago, you may want to consider seeing an allergist again. Allison Aubrey, NPR News.

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