The Remission Question
When parents find out their child is allergic to peanuts, they always ask the same question, says Katie Allen, MD, PhD: "Are they going to be one of the 20 percent who grow out of it?"
Allen is a pediatric gastroenterologist and allergist at the Murdoch
Children's Research Institute at the Royal Children's Hospital in Melbourne, Australia.
Until recently, doctors could only guess.
Now, Allen has found some good predictors by looking at skin prick test
The Skin Prick Test
In this test, commonly used by allergists, the skin is pricked and a tiny amount of the allergen is dropped onto the skin.
If the person is allergic to the substance, the body's allergic antibody, immunoglobulin E (IgE), is triggered and a chain reaction is set off, resulting in the patch of pricked skin becoming red and swollen.
This raised bump or small hive is called a wheal, and its size is known to give clues about allergies, Allen tells WebMD.
It's well-known by allergists, she says, that "kids who are 12 months old and have a skin prick with a wheal that is more than 4 millimeters means they are more than likely to have a reaction [if they eat the food they're suspected of being allergic to]."
The Remission Study
Allen and her colleagues followed 267 children with peanut allergies, some for years, to see if the size of the wheal over time could predict remission.
The children entered the study at an average age of 14 months — the time when most infants first show peanut sensitivity, Allen says.
"We looked at the size of the skin prick wheal and followed them," Allen says. Once the size of the wheal that came after a prick fell sufficiently, the scientists would give a food challenge to see if the child had outgrown the allergy.
"We found that 20 percent of them outgrew it by 5 years of age," Allen says.
"We found the best predictor of remission was a falling skin prick test
... every year the reaction got a little smaller," she says.
The size of the wheal when children are younger can predict remission, too, Allen says.
"If the skin prick wheal is greater than 6 millimeters before 2 years of age, they are 1.5 times less likely to become tolerant," she tells WebMD.
The severity of the initial reaction, however, did not predict tolerance. "Kids with severe initial reactions are as likely to outgrow it," she says, as those whose first reaction was milder.
The results offer valuable information not just for parents whose children do outgrow it, she says, but also for those whose children are not likely to and therefore may need closer follow-up.
By Kathleen Doheny
Reviewed by Louise Chang, M.D.
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