"Many people are being told that they are allergic to peanut, that they must avoid them and all foods that might contain them at all cost, are actually not allergic to the nut at all," says Swedish scientist, Professor Magnus Wickman at Sachs' Children's Hospital and Karolinska Institutet, Stockholm, Sweden. "In fact, our findings show that two out of three that are considered allergic to peanut only experience mild symptoms, if any symptoms at all. The reason is that these patients are not allergic to peanut, but to birch pollen."
"There are several different proteins in peanut that can give rise to allergic reactions. One of them, Ara h 8, is very similar to one of the proteins responsible for birch pollen allergy," adds Dr. Wickman. "What we are seeing in these patients is a mild birch pollen like reaction as a result of peanut consumption, what we call a 'cross-reaction.' Unfortunately, a routine allergy test, either in the skin or the blood, cannot tell the difference and pinpoints the patient as allergic to both peanut and birch pollen."
The problem is in the limitations of today's routine allergy tests. Normally, either a skin prick test is performed by introducing a small amount of the suspected allergen into the skin, or a basic blood test for antibodies to the allergen extract is carried out. While these tests have great utility, the problem is that neither of them can determine exactly which specific protein(s) in the extract is giving rise to the allergic reaction. To do this requires a closer look at allergy on the molecular level, at exactly which protein is causing the reaction, by testing each component separately. This is a rapidly growing area in allergy diagnostics called molecular allergology, or molecular allergy.
"Normal tests based on natural extracts from peanut or birch can only tell that the body is reacting to something in this complex mixture. Molecular allergy can precisely identify the protein that is giving rise to the reaction, making it possible to investigate the cause of allergy, discover false allergies, and find unexpected cross-reactions," says Dr. Wickman.
This is the aim of the BAMSE project, a 10-year study of over 4,000 children born between 1994 and 1996, from which this latest finding is released. The study is conducted by Karolinska Institutet in cooperation with Phadia who developed this new type of ImmunoCAP® Allergen Component tests.
"At first, as many as 7.5 percent of the children seemed allergic to peanut at age 8, based on routine tests," says Dr. Wickman. "However, using these new ImmunoCAP® tests, we were able to distinguish what peanut protein each patient was actually allergic to. This made it possible for us to see which one of them were allergic to the 'birch pollen similar' Ara h 8, and find the cross reaction."
"Clearly, these children should have been diagnosed with birch pollen allergy and not with a potentially life-threatening peanut allergy," says Magnus Wickman. "In light of these new findings and the new available allergy tests, my advice to parents of peanut allergic children is to contact their physician and ask for additional laboratory testing using allergen component testing."
ImmunoCAP® Allergen Component tests are widely used and widely available in Europe, but in the United States are available to allergy specialists only through the Phadia Immunology Reference Laboratory (http://www.pirllab.com) as a Laboratory Developed Test while Phadia works with the U.S. Food and Drug Administration to move towards clearance for ImmunoCAP Allergen Components. With Allergen Components, allergists can test patients for reactions to specific protein components of allergens.
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