PURPOSE OF THE STUDY.
To determine the influence of a variety of environmental and demographic factors on the development of challenge-confirmed egg allergy in infants.
The study included 5276 infants presenting for their 12-month immunizations in Melbourne, Australia, with a focus on 453 infants with egg allergy confirmed by oral food challenge.
At the time of initial testing, parents completed a questionnaire regarding a variety of environmental exposures and demographic factors. Infants underwent skin-prick testing (SPT) to egg regardless of history of reaction. Infants with a positive SPT then underwent additional testing, including allergen-specific immunoglobulin E testing by ImmunoCAP and an oral food challenge to egg. Infants with SPT >2 mm and positive challenge were deemed egg allergic. Multivariable logistic regression was used to determine factors associated with challenge-confirmed egg allergy. Adjustment was made for multiple confounding variables.
Factors that demonstrated a low risk for the development of egg allergy included having older siblings and having a dog in the house. Having siblings <6 years of age and having multiple siblings showed an even greater risk reduction. Factors associated with higher risk of developing egg allergy in infancy included a parent and/or sibling with a history of allergic disease and parents born in East Asia. Factors that showed no significant association included mode of delivery, antibiotic use during infancy, day care attendance, and maternal age.
This study demonstrates a lower risk for the development of egg allergy at age 1 year by having siblings and dogs in the home. Children with an immediate family history of allergic disease and having parents of East Asian (as opposed to Australian) origin show an increased risk.
This is the first large population-based study of its type using the gold standard of oral food challenge. It is not entirely surprising that sibling and dog exposure in the first year of life may be protective against the development of egg allergy. Other studies have shown that first-born children (with no older siblings) may be more likely to develop allergy. Also, pet exposure in early life might reduce the risk for respiratory allergies. These findings have been controversial, perhaps because of many confounding variables. Australian-born infants with parents of East Asian origin may represent a gene-environment interaction in which feeding habits could play a role. It is important to note that this study analyzes egg allergy at age 1. It is important to note that the authors have previously demonstrated, in the same patient population, that delayed introduction of egg (>6 months old) is a significant risk factor in development of egg allergy regardless of family history. Timing of introduction was adjusted for in this current study. It would be interesting to see if the same factors increase/decrease risk for egg allergy as this population matures.
- Copyright © 2013 by the American Academy of Pediatrics