Food allergy diagnosis ‘an inexact science’
(CNN) — Heidi Bayer knows all too well that diagnosing food allergies isn’t clear-cut.
When her daughter Phoebe Carney was 2½, her doctor did a skin test and said that she would be fine drinking milk. Hopeful, the mother gave Phoebe rice cheese with casein, a dairy product.
Suddenly, the toddler began coughing, and the color drained from her face. The mother gave her an antihistamine, but the child’s entire body turned red. That’s how they ended up in the emergency room.
“I think the tests are inconclusive, and that obviously there’s going to be instances where it looks like there has been an outgrowing of an allergy when there actually hasn’t,” said Bayer, of Brooklyn, New York. “It’s an inexact science at this point.”
It turns out that the term “food allergy” has no universally accepted definition, nor are there well-accepted criteria for diagnosis, according to a new study published in the Journal of the American Medical Association.
That means that while children like Phoebe may have life-threatening reactions to foods that don’t respond to tests, others who think they have allergies may be unnecessarily avoiding foods. There is no cure for food allergies, and doctors are unclear on why some people develop them.
“It’s a limiting diagnosis; it’s difficult socially, it’s difficult nutritionally, and so really trying to nail down whether or not you truly have an allergy is a really important thing,” said Dr. Jennifer Schneider Chafen at Stanford University School of Medicine, lead author of the study.
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Robert never had any allergies — nary a sniffle or a wheeze his entire life. Then he met his sister’s new dog, a Lab named Finn. On a recent visit, Finn’s copious dander ambushed the 39-year-old, causing sniffling, wheezing, runny eyes, scratchy throat, and relentless sneezing fits. “I’d never had reactions to any animals,” he said. “Now I won’t come in the door without drugging myself up.”
Allergists and immunologists are seeing more men like Robert, men who’ve been blindsided by new allergies. “We used to think you couldn’t develop allergies later in life,” says immunologist Donata Vercelli, M.D., a professor of cell biology and anatomy at the University of Arizona. “They usually arrived when you were young, and you typically outgrew them.”
Adult-onset allergies may be part of a broader phenomenon. Scientists call it the hygiene hypothesis: The less you’ve been exposed to allergens in your life, the more likely you may be to develop allergies as an adult, according to a 2009 Australian review in Allergy. The theory is that when your system is out of practice, it becomes sloppy, Dr. Vercelli says. Instead of idly standing by, it launches all-out attacks against harmless dander and pollen, leaving you congested, itchy, and inflamed. “Your immune system will work, not less effectively, but less appropriately,” Dr. Vercelli says.
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