Children who outgrow an allergy to peanuts but continue to avoid peanuts may be at risk of seeing the allergy reappear, a new study suggests.

Peanut allergy, which can cause severe, even life-threatening reactions, was once thought to be a lifelong problem. But in recent years, researchers have found that some children-perhaps 20 percent - eventually outgrow the allergy.

Now the new findings suggest that if these children do not work some peanut products into their diets, there is a risk of the allergy recurring.

The study found that of 15 formerly allergic children who rarely ate peanuts, three saw the allergy recur. That compared with none of 23 similar children who ate peanut-containing foods at least once a month.

Dr. Robert A. Wood, the senior author on the study, recommended that children who no longer harbor peanut allergies should eat “concentrated forms of peanut” - such as shelled peanuts or peanut butter - at least monthly.

Doing so may allow the immune system to build up a lasting tolerance to peanuts, according to Wood, a pediatric allergist at the Johns Hopkins University Children’s Center in Baltimore.

He noted that to be safe, children should always have a nearby supply of injectable epinephrine, which is used to treat acute reactions to peanuts, for one year after testing negative for peanut allergy.

A blood test for antibodies to peanut protein, as well as a food challenge test - in which children eat peanut protein under controlled, doctor-supervised conditions - are needed to confirm that a child can indeed tolerate peanuts.

If a child continues to eat peanuts only occasionally after testing deems him allergy-free, parents should keep epinephrine handy “indefinitely,” Wood said.

He and his colleagues report the findings in the November issue of the Journal of Allergy & Clinical Immunology.

Traditionally, it was thought that children diagnosed with peanut allergy face a life of reading product labels in order to avoid eating even a trace of the legume. But recent research indicates that about 20 percent of children with peanut allergy naturally outgrow it; then, in an earlier study, Wood and his colleagues found that the allergy sometimes came back.

“The recurrence was a surprise to us,” he told Reuters Health, “because it’s not something that happens with other food allergies.”

The new findings suggest that the blame lies with continuing avoidance of peanuts, because infrequent exposure to small amounts of a substance can set the stage for an allergic response, Wood noted.

One problem with getting kids to eat peanuts regularly, Wood pointed out, is that many understandably retain a “pretty strong aversion” to the food. Using cookies and candies to give children a “hidden” serving of peanuts is one way around the obstacle, according to the researcher.

For children who are not willing to eat peanut products, Wood said, allergy tests should be repeated periodically to see if the condition has recurred.

SOURCE: Journal of Allergy and Clinical Immunology, November 2004.