If your child outgrows a peanut allergy, a new study suggests he or she should eat foods containing peanuts at least once a month to prevent the allergy from returning.
Lead researcher Dr. Robert A. Wood, a professor of pediatrics at Johns Hopkins University, and his colleagues studied 68 children who had outgrown their allergy to peanuts. The purpose of the study was to find out how many of the children became allergic again. They also wanted to identify risk factors that caused the allergy to recur and to find ways to prevent it from returning.
Wood and his team evaluated repeat peanut-specific immunoglobulin-E (IgE) levels, conducted food challenges, in which the patient is given a food that he/she may be allergic to, and also had the children answer questions about what they ate.
The researchers found there was approximately an 8% chance of having a recurrence of a peanut allergy. And the risk of recurrence was much higher among children who avoided eating peanuts after they had outgrown the allergy, the research group reports.
According to the results of the research, eating something containing peanuts at least once a month helps maintain a tolerance. Although the allergy apparently does not recur if the amount of peanuts eaten is limited, children should carry epinephrine just in case a reaction develops. "It is much less likely to get the allergy back if you are eating peanut products on a regular basis once you have been able to tolerate peanut (products],” Wood says.
"We were surprised a few years ago to discover that some children who had lost their peanut allergy got it back," says Wood. "That is something we had not seen with other food allergies.
Wood says a peanut allergy is not unique—the same thing happens with other food allergies, such as milk or eggs. The big difference is that when people outgrow their milk allergy, they are probably still getting milk protein in their diet on a daily basis, he says, even if they don't drink much milk. Dairy is found in many products that are commonly consumed in the diet, and repetitive exposure, as with peanuts, can build resistance.
"It is common for people who have had a peanut allergy to still avoid the food even though we have told them they can put it back into their diet," Wood says. Yet, "we now recommend that our patients eat concentrated forms of peanut at least once a month after outgrowing their peanut allergy, in an attempt to maintain peanut tolerance."
"While a peanut allergy was often considered to be lifelong, studies from several centers have shown that about 20% of young children with the allergy are able to consume peanut [products) at school age," states Dr. Scott H. Sicherer, an associate professor of pediatrics at the Jaffe Food Allergy Institute at Mount Sinai School of Medicine. "This exciting discovery is tempered by the observation, reported by our group and several others, that some of the children eventually had a recurrence of the allergy," he adds.
When a child successfully ingests peanut products, but continues to avoid them, he or she faces an increased risk that the allergy could recur. "We have them continue to have emergency medication available for a year or two until it is clear the child is eating peanut (products) routinely. If the child refuses to eat peanut (products), we would need to test him/her periodically to know if a danger has reemerged," Sicherer says.
Wood's team agrees. They recommend that patients and families who eat peanut products frequently continue to carry injectable epinephrine for at least one year after eating peanuts without having an allergic reaction. "If they eat peanut (products) only infrequently or in limited amounts, then patients should have epinephrine available indefinitely at all times because of their increased risk of recurrent allergy," the researchers conclude.
Wood notes that all allergies are on the rise in developed countries but are almost unheard of in developing countries. Part of this increase can be explained by the hygiene theory, he says. "The less infants are exposed to germs and infections, the more their immune systems can focus on things like allergies. Allergies are much less common if you grow up on a farm [or] have close contact with animals. The more exposure you have to bacteria and other infections early in life, the less likely you are to have allergies," he says.