“About 9 percent of kids will test positive for peanut allergies if tested,” Sicherer said, but only 1 percent actually develop full-blown allergic reactions when they eat peanuts. “The tests that we have available today are excellent,” he added, “but they have to be ordered and interpreted appropriately.”
Children who develop hives after eating an almond cookie, for example, should be tested for nut allergies if they’ve never eaten nuts before, but shouldn’t be tested for a wheat allergy if they’ve already been eating bread without a problem.
To complicate matters even more, some kids develop itchiness in their mouths when they eat certain raw produce like carrots, peaches, and apples and will — like Blumenfeld — test positive for allergies to these foods when they’re primarily allergic to birch pollen. That’s because there are proteins in these raw foods (which break down when they are cooked) that are similar to proteins in the pollen.
“We don’t think kids who have milder food allergies related to a protein in birch pollen are at risk of having a serious reaction, like anaphylactic shock, to these foods,” said Shreffler, who is Blumenfeld’s physician.
Some allergists have begun using newer tests — like those that look for reactions to birch pollen allergens — to distinguish between pollen allergies and true food allergies. Blumenfeld’s father, Josef, said the test wasn’t covered by his insurance but was the “best $300” he’d ever spent.
“To hear she wasn’t allergic to all these foods?” he added. “It was incredibly liberating.”
Newer blood tests that are more specific might be able to better predict who is more likely to have a life-threatening reaction to a food challenge — when children are given a small amount of a food to see if they develop a reaction — to determine whether they are still allergic to a particular food. But most community allergists aren’t using the tests because they are experimental.
John Kozelian of Belmont said his daughter’s first allergist felt uncomfortable administering a food challenge to see whether his daughter Olive was still allergic to milk because she had developed a mild rash when given a skin test. So two years ago, he took Olive to Massachusetts General Hospital, where they were using the experimental blood tests.
“Based on that blood test, they felt comfortable about doing a food challenge,” Kozelian said. To 12-year-old Olive’s delight, she learned she had outgrown her milk allergy; last year, she found out from a food challenge that she could also eat eggs.
“We were able to buy her a store-bought birthday cake with eggs and butter,” said Kozelian. “We’d given up thinking she would outgrow her allergies since that’s what we’d been told by her initial doctor.”
Deborah Kotz can be reached at email@example.com. Follow her on Twitter @debkotz2.