Food Allergy False Positives

So the common test of determining food allergy has questionable results, why is it still being used then? I always suspect the profit motive – pediatricians need that second condo in Aspen too…


Grayson Grebe started getting eczema on his cheeks when he was just 4-weeks-old. At 6 months, he was diagnosed with allergies to wheat, dairy, eggs, nuts, oats, rice, barley, chicken, pork, corn and beans; his mother, who was breast-feeding him, had to stop eating them all. At 10 months, doctors cut out 20 more foods, including all fruits and vegetables, and put Grayson on a hypoallergenic formula. Even so, his eczema was so bad that his parents put him in mittens, long-sleeved shirts and long pants so no skin was exposed. “Otherwise, he’d scratch himself until he would bleed,” says his mother, Amy Grebe of Albuquerque, N.M.

At wit’s end, the Grebes took Grayson to National Jewish Health, a hospital in Denver that specializes in allergies and respiratory diseases. Doctors there suspected that his food allergies might not be causing the eczema—and that some might not be food allergies at all. After carefully supervised “food challenges”—giving him tiny amounts and monitoring him closely for signs of a reaction—a number of foods went back in his diet. “We came home with 12 foods he could eat,” says Amy Grebe. “It’s made so much difference in our lives.”

For parents of children with food allergies, this may be both welcome and unsettling news: Many kids whose allergies were diagnosed on the basis of blood or skin tests alone may not be truly allergic to those foods, experts say.

Blood tests measure the level of antibodies, called immunogloblin E (IgE), a body makes to a particular food. But having IgE antibodies doesn’t mean that a person will actually have an allergic symptom when he encounters it.

The only way to know for sure—short of encountering the food in real life—is with a food challenge test in a doctor’s office or hospital. But those can be time consuming, expensive and nerve wracking, especially for parents who have seen a child encounter an anaphylactic shock, a life-threatening reaction in which multiple organs quickly shut down.

[Click to continue reading When Is Your Kid’s Food Allergy Really a Food Allergy? –]
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Big Pot of Smiley Faces

Not that doctors are being malicious, they just are erring on the side of caution, using tools that are notoriously imprecise, responding to worried parents.

“Are these blood tests being overused? Possibly. Misinterpreted? Absolutely,” says Robert Wood, director of Pediatric Allergy and Immunology at Johns Hopkins Hospital, who is part of a task force writing guidelines for diagnosing and managing food allergies. “A lot of these kids truly have food allergies, just not to all the foods that they are being told they have allergies to.”

In some cases, the blood or skin tests reveal antibodies to a food that the child has already been eating without problems. It’s easy to dismiss those results. It’s harder to know what to make of IgE antibodies to foods a child hasn’t yet tried. Children with eczema, like Grayson Grebe, tend to have IgE antibodies to a large number of foods, and it can be difficult to sort out which really do pose problems.

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