Published Online: February 25, 2015
IgE-mediated peanut allergy affects one-and-a-half to three percent of children and is the food allergy most often associated with severe and fatal allergic reactions. The prognosis of peanut allergy is poor with only a small proportion of children expected to outgrow their allergy. This assertion is generally based upon retrospective audits of allergy clinic records and has never been assessed in a large-scale, prospective, population-based study. In addition, clinical predictors of when and in whom tolerance to peanut will develop are lacking. Identification of such predictive factors will improve patient management and care.
Recently, in The Journal of Allergy and Clinical Immunology (JACI), Peters et al have published the first prospective, population-based study on the natural history of peanut allergy. The HealthNuts study recruited 5,276 twelve-month-old infants and skin prick tested them to common food allergens including peanut. Any infant who was sensitized to peanut was invited to have an oral food challenge (OFC), the gold standard test for the diagnosis of peanut allergy. Peanut allergy was confirmed in 156 infants. At the age of four these children were invited to undergo repeat OFC to test for whether they had outgrown their peanut allergy.
Overall, the study found that 22% of children outgrew their peanut allergy by four years of age. Skin prick testing (SPT) and blood tests for peanut-specific IgE (sIgE) are commonly used to monitor the course of peanut allergy, although thresholds for these tests which predict whether peanut allergy has persisted or resolved are unknown. This study reported that at age four, children with SPT ≥ 8mm and sIgE ≥ 2.1kU/L had a 95% probability of remaining allergic to peanut, while children with SPT ≤ 2mm had a 90% probability of having developed tolerance.
A novel finding was that SPT and sIgE measured at 12 months of age was also able to predict which infants would still be allergic to peanut at the age of four. Infants with SPT ≥ 13mm or sIgE ≥ 5.0kU/L at age 12 months had a 95% probability of having persistent peanut allergy at age 4 years. Despite considering multiple other prognostic factors, (including tree nut and house dust mite sensitization, coexisting food allergies, eczema, and asthma) no other clinical predictors of the development of tolerance could be identified.
These thresholds are the first to be generated from a population-based study in which all participants underwent OFC at both diagnosis and follow-up and are a valuable tool for the management of peanut allergy. They will be useful in reducing the need for unnecessary OFC in children with a high risk of persistent peanut allergy.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.