The Natural History of Peanut Allergy in Young Children and Its Association with Serum Peanut-Specific IgE

Abstract

Purpose of the Study. To characterize adverse reactions after accidental peanut exposure in young children with peanut allergy and to determine the usefulness of serum peanut-specific immunoglobulin E (IgE) levels during follow-up.Study Population. One hundred two children were identified who had clinical peanut hypersensitivity before 4 years of age. Inclusion criteria included 1) a convincing history of clinical peanut hypersensitivity and/or a positive double-blind, placebo-controlled food challenge (DBPCFC) response to peanuts and 2) a positive skin prick test response to peanuts.Methods. Research subjects were contacted at least yearly to track adverse reactions caused by accidental exposure to peanuts. Nineteen participants discontinued their participation in the study or were lost to follow-up, leaving 83 for inclusion in the analysis. Peanut-specific serum IgE levels were determined in 51 of 83 subjects using the Pharmacia CAP system (Uppsala, Sweden).Results. Thirty-one of 53 (58%) of the subjects followed for 5 years experienced adverse reactions from accidental peanut exposure. Regardless of the nature of their initial reaction, the majority with subsequent reactions (31/60; 52%) experienced potentially life-threatening symptoms. The group with isolated skin symptoms (11/51; 22%) had lower serum peanut-specific IgE levels (median: 1.25 kUa/L vs 11.65 kUa/L; P = .004; Wilcoxan rank sum) than the group with respiratory and/or gastrointestinal symptoms (40/51; 78%). There was no threshold level below which only skin symptoms appeared to occur. Of note, 4 subjects had negative DBPCFC results to peanuts during the follow-up period.Conclusions. The majority of children with peanut allergy followed for up to 5 years will have adverse reactions from accidental peanut exposure. Symptoms may not be consistent with symptoms reported during initial reactions. A minority of children with peanut allergy can lose their clinical hypersensitivity.Reviewer’s Comments. This report addresses 2 common questions asked by parents of children with peanut allergy: a) will the reactions become progressively worse? and b) will the reactions ever subside? Despite appropriate counseling on peanut avoidance, the majority of the children experienced an accidental peanut ingestion during follow-up. Moreover, initial clinical reactions involving only the skin can subsequently progress to involve the respiratory and/or gastrointestinal systems. A minority of subjects with low serum peanut-specific IgE levels developed oral tolerance to peanut. This investigation has expanded the growing body of evidence in this research area and has provided practical clinical information for addressing allergic reactions to peanuts. With the inevitability of accidental ingestions, the general trend for worsening of clinical reactions with subsequent exposures, and the inability to predict severity of future reactions, the take-home messages should be that all patients with peanut allergy need proper education about the potential seriousness of future accidental exposures and self-injectable epinephrine to manage future, severe allergic reactions.