The natural history of peanut allergy

Background: It has traditionally been assumed that peanut allergy is rarely outgrown. Objective: The goal of this study was to determine the number of children with peanut allergy who become tolerant of peanut. Methods: Patients aged 4 to 20 years with a diagnosis of peanut allergy were evaluated by questionnaire, skin testing, and a quantitative antibody fluorescent-enzyme immunoassay. Patients who had been reaction free in the past year and had a peanut IgE (PN-IgE) level less than 20 kilounits of antibody per liter (kU_A/L) were offered an open or double-blind, placebo-controlled peanut challenge. Results: A total of 223 patients were evaluated, and of those, 85 (PN-IgE < 0.35-20.4 kU_A/L [median 1.42 kU_A/L]) participated in an oral peanut challenge. Forty-eight (21.5%) patients had negative challenge results and were believed to have outgrown their peanut allergy (aged 4-17.5 years [median 6 years]; PN-IgE < 0.35-20.4 kU_A/L [median 0.69 kU_A/L]). Thirty-seven failed the challenge (aged 4-13 years [median 6.5 years]; RAST < 0.35-18.2 kU_A/L [median 2.06 kU_A/L]). Forty-one patients with PN-IgE levels less than 20 kU_A/L declined to undergo challenge, and 97 were not eligible for challenge because their PN-IgE levels were greater than 20 kU_A/L or they had had a recent reaction. Sixty-seven percent of patients with PN-IgE levels less than 2 kU_A/L and 61% with levels less than 5 kU_A/L had negative challenge results. Of those who underwent challenge, PN-IgE levels for those who passed versus those who failed were different at the time of challenge (P =. 009), but not at the time of diagnosis (P =. 25). Conclusion: This study demonstrates that peanut allergy is outgrown in about 21.5% of patients. Patients with low PN-IgE levels should be offered a peanut challenge in a medical setting to demonstrate whether they can now tolerate peanuts.