A.W. Burks

The 2S albumin allergens of Arachis hypogaea, Ara h 2 and Ara h 6, are the major elicitors of anaphylaxis and can effectively desensitize peanut-allergic mice.

Ara h 2 and Ara h 6, co‐purified together in a 13–25 kD fraction (Ara h 2/6; 20 kD fraction) on gel filtration chromatography, account for the majority of effector activity in a crude peanut extract (CPE) when assayed with RBL SX‐38 cells sensitized with IgE from human peanut allergic sera.

How do we know when peanut and tree nut allergy have resolved, and how do we keep it resolved?

Over the last two decades, the prevalence of peanut and tree nut allergy has increased throughout the western world. Adverse reactions to these foods account for over 50% of all deaths resulting from food‐related anaphylaxis. Until recently, evidence suggested that all peanut and tree nut allergy were permanent. It is now known that about 20% and 10%, respectively, of young patients outgrow peanut and tree nut allergies. Achieving tolerance is associated with increasing circulating T regulatory cells and reduced production of allergen‐specific IgE. Reliable predictors of resolution are not yet available. A direct correlation between skin test weal size and allergen‐specific IgE, at the time of diagnosis and likelihood of resolution, has been reported. Resolution of peanut or tree nut allergy cannot be determined conclusively by either allergen‐specific IgE analysis or by skin prick testing. Oral food challenge is the gold standard for determining resolution of food allergy. Food challenges should only be undertaken in a clinical setting fully equipped to deal with a potential severe adverse reaction. Approximately 8% of patients who outgrow peanut allergy may suffer a recurrence, but recurrent tree nut allergy has not been reported to date. Infrequent ingestion of peanut may be related to the re‐emergence of allergy. Induction of tolerance through oral immunotherapy or sublingual immunotherapy is now being actively studied, but remains experimental. Studies have reported short‐term desensitization to peanut, but ongoing follow‐up will determine whether tolerance is achieved long term.

265 THE NATURAL HISTORY OF FOOD ALLERGIES IN CHILDREN: AN EVALUATION OF CLINICAL TOLERANCE AND SEVERITY OF REACTIONS TO FOOD CHALLENGES

Purpose To compare food-specific IgE levels and age of passed or failed oral food challenges (FC) and examine the severity of failed FC. Methods We performed a retrospective review of food allergic patients who underwent milk, egg, soy, wheat, and peanut FC (January 2000-June 2004) based on known predictive IgE levels. Food-specific IgE and age were determined for those who passed or failed challenges. System involvement and treatment of failed challenges were analyzed. Results One hundred sixty-three FC were performed in 106 patients (67% male; 83% Caucasian; 66% atopic comorbidities). 56% of FC were blinded, 43% open. Negative challenges occurred in 97/163 (60%) - milk 47%, egg 61%, peanut 66%, soy 61%, and wheat 63%. Median age (years) of those passing challenges was: milk 3.2; egg 4.5; peanut 5.1; soy 2.3; wheat 3.6. For failed challenges median age was milk 2.0; egg 4.4; peanut 4.0; soy 4.6; and wheat 4.0. Median food-specific IgE levels (kUA/L) for passed FC were milk 1.6; egg 0.7; peanut 0.7; soy 0.7; and wheat 6.7. IgE levels for failed challenges were milk 4.5; egg 0.7; peanut 1.4; soy 20; and wheat 7.5. For failed challenges, 80% had cutaneous involvement, 32% upper respiratory, 23% lower respiratory, and 32% gastrointestinal. Positive challenges were successfully treated with antihistamines (80%), bronchodilators (8%), charcoal (2%), epinephrine (11%), and fluids/corticosteroids (2%), while 8% required no treatment. Conclusions For patients with low food-specific IgE levels approaching 95th% negative predictive value, FC can be performed safely, with minimal symptoms and with the majority of patients showing clinical tolerance.