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February 9, 2001
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Twenty Percent May Outgrow Peanut Allergy, Scientists Reveal

People who live in fear of their peanut allergy, anxiously avoiding numerous products and worrying that accidental exposure could cause a severe or even fatal reaction, may be cheered to learn that they may outgrow it, according to a study by Johns Hopkins researchers reported in the February issue of the Journal of Allergy and Clinical Immunology.

"In our patient group, roughly 20 percent outgrew their peanut allergy," says Robert Wood, M.D., associate professor of pediatrics at Johns Hopkins and lead investigator of the study. He cautions, however, that people should only be tested and reevaluated under a doctor’s care before abandoning preventive or avoidance measures.

"Until now, the rules have been that when you diagnose a patient with peanut allergy, tell them that it is a life-long allergy, with no chance of being outgrown," says Wood. "I recommend from this study that children with peanut allergy be retested on a regular basis, every one or two years." Adults who have not had any reactions since childhood and who have never been retested should also be reevaluated, according to Wood, who has peanut allergy himself and whose own retest disappointingly found he still is allergic.

In a study of 223 people with well-documented peanut allergy from Hopkins, the Arkansas Children’s Hospital and Wood’s private clinic, scientists discovered that 48 did not have an adverse reaction after eating 4 grams of peanut protein. The researchers found that people were more likely to outgrow their peanut problem if they had lower levels of peanut specific IgE, antibodies produced by the immune system that cause allergic reactions. When exposed to peanut proteins, these antibodies, which sit on the surface of allergy (mast) cells, trigger symptoms such as hives, swelling, vomiting or difficulty breathing. Children who had lost sensitivities to other foods, including milk or egg, were also more likely to outgrow peanut allergy.

The allergy, which can be triggered by a mere 1/1000 of a peanut, causes the most severe reactions of all food allergies and is estimated to kill approximately 100 people per year. Allergic individuals carry a tremendous burden of fear, anxiously attempting to avoid the remarkable number of products that contain peanuts, peanut flour or peanut derivatives. This includes steering clear of many cookies, crackers, chips, cereals, baked goods and Asian foods, as well as making sure that a cooking utensil contaminated with peanut residue or oils is not used to prepare one of their foods. Because allergy shots do not work (they create too much risk of a severe reaction), people who are allergic to peanuts are advised to carry an epinephrine shot with them at all times in case of anaphylaxis, the life-threatening allergic reaction that can constrict airways in the lungs, severely lower blood pressure, and cause swelling of the tongue or throat, literally suffocating victims.

Prior to this study, when doctors retested children for allergies, they found that while many outgrew their allergies to milk, egg, soy and wheat, peanut allergy remained as strong and potent, year after year. Wood and his colleagues, however, recognized a few cases that did not follow this pattern. "We saw a few allergic people who did not react when they had an accidental exposure or when they were retested as part of our normal follow-up of food allergies," says Wood. "We were interested in finding out how many people outgrew their allergy and if we could predict who was going to outgrow it. Food allergies often travel together, so we tested other food allergies along with peanut allergy."

The doctors identified patients with peanut allergy, ages 4 to 20 years, and investigated their initial and subsequent reactions to peanut, as well as their history of other allergies. The volunteers then underwent skin testing, which measures redness and swelling after pricking the skin with an allergen, in this case peanut. They also measured the level of peanut specific IgE in the patient’s blood. Those who met specific criteria, principally a peanut IgE level below a certain point, were invited to undergo an oral challenge under a doctor’s supervision.

On the basis of past experience and IgE levels, 126 patients were eligible for an oral peanut challenge. Out of the 85 people who agreed to participate, 48 had no adverse reaction. This means that over 20 percent of all the children studied had lost their allergy. Wood also said that since the formal completion of the study, he has identified at least 20 additional children who have outgrown their peanut allergy.

"People who may have outgrown their allergy, based on the criteria established in this study, should definitely go through a formal oral challenge under a doctor’s supervision," says Wood. "Relieving the burden of fear that is caused by a peanut allergy is easily worth going through the challenge."

Wood next plans to monitor children from their initial diagnosis in an attempt to pinpoint other signs that will indicate which people are more or less likely to outgrow the allergy. For more information about asthma and allergy research at Johns Hopkins, visit http://www.hopkins-allergy.org.

The study was funded by the National Institutes of Health, the Eudowood Foundation for the Consumptives of Maryland, the National Center for Research Resources, Johns Hopkins University School of Medicine General Clinical Research Center, and the Food Allergy Initiative. Other authors of the study include Helen Skolnick, Mary Kay Conover-Walker and Celide Barnes Koemer from Johns Hopkins; Hugh Sampson from Mount Sinai Hospital; and Wesley Burks from the University of Arkansas for Medical Sciences.

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