Introduction
Food allergies pose a significant public health concern due to their increasing incidence in infants and children in the last few decades worldwide, and particularly in industrialized countries.1,2 Emerging treatments, including oral and epicutaneous immunotherapy for food allergies, are still considered investigational because of safety concerns and uncertain long-term efficacy.3 Thus, the conventional management for patients with food allergies remains strict avoidance of the allergenic food and being prepared for any adverse reactions from unintended food ingestion.4 Since many children with a food allergy outgrow the disease,5 a practical strategy is to wait for “the day of resolution” by observing the current management principle.
Recently, however, observations that dietary inclusion of baked hen’s egg or cow’s milk accelerated resolution of egg or milk allergy have attracted attention.6-11 Although evidence for the potential of baked products to promote outgrowing the disease still awaits well–designed randomized controlled studies,12partial liberalization of a child’s diet may be beneficial due to the improved quality of life and nutritional status.13
To ascertain the safety of implementing such diet liberalization, it is necessary to first perform oral food challenge (OFC) to determine the quantity of food that a patient can consume without triggering an allergic reaction. In the baked egg/milk diet, a patient must pass an OFC with baked egg containing 1 whole egg6,7 or baked milk containing 0.5–1.3 g of milk protein (equivalent to 15–40 mL of milk).8-11 The allergenicity of the baked products is assumed to be reduced, but children who nevertheless react to that quantity of allergen should completely avoid the food. However, they may safely consume a lesser amount of the allergen—such as 10 g of butter (equivalent to 2.9 mL of milk)—than that in the recommended baked diet.14 In Japan, the national health insurance covers OFC testing, and guidelines15 provide dietary guidance on how to consume a small, safe amount of an allergenic food based on the results of readily available OFC using a low dose of allergen. Dietary liberalization is now increasingly recommended and performed in pediatric practice in Japan.
This new approach to management of food allergy seems to be beneficial to the patients. The natural course of food allergy, however, varies widely from tolerance to persistence,5 which may affect results of the management. Reported predictors of persistence of a food allergy in the natural course include a history of anaphylaxis, the presence of another food allergy, comorbid allergic diseases such as asthma, reaction to even a low dose, elevated allergen–specific IgE (sIgE) levels, etc.5,16,17 In addition, it was reported that mothers with a high level of anxiety, even after a negative OFC for their child, were reluctant to reintroduce the offending food.18 Psychological factors may affect the natural history of food allergy.
We therefore designed and conducted the IQ–OFA (Impact of QoL on Outgrowing Food Allergy) study to identify factors that are associated with natural outgrowing of food allergies in children, with special focus on the QoL. In the current study, we aimed to investigate factors related to successful reintroduction of egg to the diet of egg–allergic children after OFC–based dietary advice. Our findings may contribute to children’s ability to naturally outgrow food allergies.