Introduction
Cow’s milk allergy (CMA) is one of the most common food allergies in infants, with a global prevalence of 2–3%.1-6 In Japan, cow’s milk (CM) is the second major food allergen, with a proportion of 21.8% of causative foods.7
Previous studies have reported that approximately 50–90% of children with CMA acquire tolerance by pre-school age.8-10Regarding the natural history of CMA beyond school age, a CMA resolution rate of 97% by the age of 15 years was reported in a birth-cohort study from Denmark.11 A longitudinal study in the USA reported that the CMA resolution rate was 42%, 64%, and 79% by 8, 12, and 16 years of age, respectively.9 However, these studies started follow-up in infancy, and there are no studies on the natural history of CMA that persist beyond school age.
Higher levels of CM-specific immunoglobulin E (sIgE), larger wheal sizes in skin prick tests, the presence of anaphylaxis, more severe atopic dermatitis, and coexisting bronchial asthma and allergic rhinitis have been reported as risk factors for the persistence of CMA in infants.8-10, 12-14 However, these factors were based on the results of studies in which follow-up started in infancy; thus, the risk factors associated with CMA that persists beyond school age are unknown.
Therefore, we aimed to investigate the tolerance acquisition rate in children with CMA persisting from the age of 6 years until the age of 12 years, as well as the factors affecting its persistence.