This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. It was once thought that nut allergy, including peanut and tree nuts (walnut, almond, cashew, pecan, Brazil nut, hazelnut, pistachio, pine nut, and macadamia nut), was a lifelong problem. Recent studies have shown that about 20% of children outgrow their peanut allergy, but there have been no studies performed to determine how many children with tree nut allergy will outgrow it. We hypothesize that a significant number of children with early onset tree nut allergy will become tolerant of tree nuts later in childhood. We also hypothesize that the RAST (radioallergosorbent test), which measures food-specific IgE levels, will be the most useful predictor of clinical reactivity to tree nuts, and that we will be able to predict the odds of passing an oral challenge at different specific IgE levels. Two to four hundred patients aged 0 - 21 years who have been diagnosed with tree nut allergy, either by clinical history of an allergic reaction after ingestion, or by history of a positive tree nut skin test or specific IgE level without prior ingestion, will be recruited from the Pediatric Allergy Clinic at Johns Hopkins and Dr. Wood's private practice. Demographic and clinical information, including the patient's age, sex, initial symptoms, skin test results, RAST results, food challenge results, other food allergies, and associated atopic diseases such as asthma, allergic rhinitis, or atopic dermatitis, will be collected. Patients who consent for the procedural phase of the study will complete a detailed questionnaire and undergo a history, physical exam, and skin and RAST testing to tree nuts. All patients aged 4 years or older who have not had a reaction to a tree nut in the past year and who have all tree nut-IgE levels less than 10 kU/L will be offerred double-blind, placebo-controlled food challenges (DBPCFC). The DBPCFCs will be deferred and the patient will be deemed tree nut-allergic if any one of the tree nut-IgE levels are greater than 10 kU/L, the patient has failed a previous tree nut challenge in the past year as part of their routine care, or the history of a recent reaction after accidental exposure is convincing enough that a challenge would be unnecessary and potentially dangerous. We expect that between 10 and 20% of children outgrow their tree nut allergy. We believe that we will find that tree nut-IgE levels are the best guide to determine which patients merit challenge. Upon completion, we will be able to provide clear guidelines for both patients and clinicians on the natural history of tree nut allergy, the value of re-evaluation over time, and the appropriate use of oral food challenges.
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