Some children may outgrow life-threatening peanut allergy, researchers find
HELEN BRANSWELL, Canadian Press
Thursday, July 10, 2003
TORONTO (CP) - Some children who are allergic to peanut may actually outgrow the life-threatening allergy, some American researchers have reported.
A simple blood test could be used to identify which children may have outgrown their allergies, the researchers say. Those who have low levels of peanut-specific antibodies circulating in their blood could then be given a "peanut challenge" under controlled circumstances to see if they are still allergic.
"Although we once thought peanut allergy was a life-long problem, we now believe certain children, namely those with low levels of allergy antibodies, may outgrow it," Dr. Robert Wood, pediatric allergist and immunologist at Johns Hopkins Children's Center in Baltimore, said Thursday.
Wood, who was the senior author on the study, said based on the findings he now recommends that children with peanut allergy be retested every year or two.
The study, a collaboration between researchers at Johns Hopkins and Arkansas Children's Hospital, were published in the July issue of the Journal of Allergy and Clinical Immunology.
Allergy to peanut is one of the most dangerous of food allergies, both because peanut products are widely used in the manufacture of processed foods and because even minute amounts of peanut protein can be enough to trigger potentially fatal anaphylactic shock.
Parents of children with peanut allergy live in fear, forced to examine every label of every food item entering a household to ensure they pose no threat to their children.
"It's very tough," said Laurie Harada, executive director of Anaphylaxis Canada, a not-for-profit organization that provides information on deadly allergies. "There is a way to eat safely, but it's all about reading, reading, reading ingredients." But if Wood and his colleagues are right, the diagnosis of a peanut allergy isn't a life-long sentence for all who receive it.
"It is a challenge to live with a life-threatening allergy, so it certainly provides some hope for those who do have it," Harada said of the findings.
The researchers studied 80 children aged four to 14 with well documented peanut allergies. The children had first been given a blood test to check their levels of peanut-specific IgE, the antibodies found in those people with peanut allergy. IgE readings are measured on a scale of zero to 100.
"What we've found is that if your level is above 10, it's a virtual guarantee that you're (still) allergic to peanut," Wood said in a telephone interview.
"And if your level is less than five, there is increasingly high chance that you're no longer allergic to peanut." This group of children was selected because they all head IgE readings of five or under.
They were then given an oral peanut challenge, which is a common diagnostic tool for allergies. Subjects are fed small amounts of peanut under strict observation, with all necessary medical equipment at hand in case a severe reaction occurs. Such challenges should only be done under medical supervision.
More than half of the children - including some who had failed a previous peanut challenge - tolerated the challenge and were therefore considered to have outgrown the allergy, the researchers reported.
Interestingly, there was no way of predicting from the children's earlier reactions to peanut which would outgrow the allergy.
"We thought at the beginning we would be able to predict people more accurately by things like that. And it turned out that there are really no good predictors of who may outgrow it, except that blood test," Wood said.
In a separate component of the study, the researchers followed up on 64 children who had been deemed to have outgrown their peanut allergy to see if they had incorporated peanut into their diet and had been able to tolerate it over time.
Most ate it infrequently and in small amounts, though some avoided it entirely.
"The biggest reason for it was actually not the parents' fear, but the child's aversion," Wood said.
"They either, because of not acquiring the taste, but more likely because of the fear that they'd lived with up until that point, really didn't want to have much of anything to do with it." Rather than making them safer, this behaviour could actually be undermining their safety, the researchers believe, suggesting that in order to maintain tolerance, former peanut allergy sufferers should actually consume some peanut products on a regular basis.
"That's what we think," Wood said.
The study was funded by the U.S. national institutes of Health and Allergy Infectious Disease, as well as the Eudowood Foundation for the Consumptives of Maryland and the Myra Reinhard Family Foundation.
© Copyright 2003 The Canadian Press.