AAAAI: Finding the Peanut in the Haystack

SAN DIEGO, Feb. 26 -- It may be possible to predict which children with peanut allergies will eventually outgrow them and become goober tolerant, according to Australian investigators.

In a study of infants and toddlers with peanut allergies who were followed for up to nine years, patterns in immunoglobulin E levels and the diameter of wheals raised on skin prick testing were predictive of whether peanut allergies would go into remission, reported Katie J. Allen, M.D., Ph.D., and colleagues, of the Royal Children's Hospital in Parkville.

"One of the first questions that parents ask when their child is diagnosed with peanut allergy is whether the child will grow out of it, said Dr. Allen at the American Academy of Allergy, Asthma & Immunology meeting here. "It's obviously of concern to them, and a lot know that a small proportion will not have lifelong peanut allergy."

Although peanut allergy remission has been well documented, there are few known predictors of remission, Dr. Allen and colleagues reported in poster session.

To see whether they could identify early clinical predictors of allergy, the investigators identified children younger than two years old who were referred consecutively for presumed peanut allergy, on the basis of an unequivocal history of allergic reactions, and/or skin prick test wheal size more than 95% likely to predict a clinical reaction to peanut.

The authors performed skin prick testing at baseline and then yearly until either levels were below those that were more than 95% likely to predict a clinical reaction to peanut, or when a child accidentally ingested peanuts and was able to tolerate them.

They found that 21% of the children had remission of presumed peanut allergy by age five, and that prognosis of peanut allergy could be predicted by either a constant rise, or constant fall in the level of immunoglobulin E (IgE) sensitization to peanut by age three.

The investigators determined that a children are two to three times less likely to develop tolerance to peanuts if they have a wheal diameters on skin prick testing that are 6 mm or larger before age two.

"A 3 mm or greater rise of skin prick test wheal size between one and four years of age was strongly predictive of persistent peanut allergy," Dr. Allen said, "whereas as falling levels was a good prognostic sign."

Neither the severity of the initial clinical reaction, gender, age at diagnosis, total IgE levels, co-morbidities with asthma nor other food allergies or early inhalation allergen sensitization were associated with prognosis of peanut allergy, the investigators found.

In addition, although allergies to tree nuts and to sesame were more common in the group of children who remained allergic to peanuts, neither of these former sensitivities were predictive of the rate of remission.

The authors concluded that the "size and annual rate of change of skin prick testing over time can be helpful in predicting peanut allergy remission."

They also found that, despite active peanut avoidance, including intensive education and an action management plan for each child, 20% of the children still accidentally ingested peanuts.

"Avoiding peanuts is difficult for children, even when they're trying hard to do it," Dr. Allen said.