There is no prospectively collected data available on the natural history of peanut allergy in early childhood. Previous studies have been biased by failure to challenge high-risk children when IgE antibody levels are high, potentially biasing towards persistent allergy. We sought to describe the natural history of peanut allergy between ages 1 and 4 years and develop thresholds for skin prick test (SPT) and serum specific-IgE (sIgE) that have 95% positive predictive value (PPV) to persistent peanut allergy.
Challenge-confirmed peanut allergic 1-year-old infants (n=156) from the population-based, longitudinal HealthNuts Study (n=5276) were followed up at 4 years of age with repeat oral food challenge, SPT and sIgE (n=103). Challenges were undertaken at both ages 1 and 4 years, irrespective of risk profile.
Peanut allergy resolved in 22% (95% CI 14-31%) of children by age 4 years. Falling wheal size predicted tolerance while increasing wheal size was associated with persistence. Thresholds for SPT and sIgE at age 1 with 95% PPV to persistent peanut allergy are SPT ≥ 13mm and sIgE ≥ 5.0 kU/L. Thresholds for SPT and sIgE at age 4 with 95% PPV to persistent peanut allergy are SPT ≥ 8mm and sIgE ≥ 2.1 kU/L. Ara h2, tree nut and house dust mite sensitisation, coexisting food allergies, eczema and asthma were not predictive of persistent peanut allergy.
These thresholds are the first to be generated from a unique dataset where all participants underwent OFC at both diagnosis and follow-up, irrespective of SPT and sIgE.