PURPOSE OF THE STUDY.
Earlier guidelines, in which delaying the introduction of potentially allergenic foods to infancy in an effort to prevent food allergy was recommended, were based on little evidence. These researchers sought to determine if the development of egg allergy by 12 months of age is associated with the age at which egg and solids are introduced and the duration of breastfeeding.
Subjects aged 11 to 15 months were recruited during immunization visits as part of the Australian HealthNuts study, which was a single-center, population-based, cross-sectional study of food allergy.
During the clinic wait period after immunization, skin-prick tests for egg white, saline, and histamine were administered. Before the results were read, a questionnaire was administered to the parents regarding age of egg introduction. A second self-administered questionnaire collected information regarding duration of breastfeeding and age of solids introduction. Infants with positive skin-prick-test results to egg (wheal size ≥1 mm greater than negative saline control) were offered oral food challenges within the next 4 to 8 weeks. Infants with a history of reaction to egg in the previous month and/or a positive skin-prick-test result who were currently avoiding egg were considered egg allergic and excluded from oral food challenges.
Of 3552 eligible infants, 2589 (73%) were recruited. Results of egg skin-prick tests were positive for 448 infants, and 340 infants underwent an oral food challenge. Overall, 231 infants (8.9%) were determined to be egg-allergic. Egg introduction at 4 to 6 months was associated with a decreased risk of egg allergy, whereas egg introduction after 10 months was associated with an increased risk of egg allergy in both low- and high-risk infants. High-risk infants with a family history of allergy or a personal history of food allergy or eczema had a much higher risk of egg allergy (odds ratio [OR]: 6.7 [95% confidence interval (CI): 4.7–9.6]). Age of introduction of cooked egg (boiled, scrambled, fried, or poached) was significantly associated with egg allergy, whereas age of introduction of baked egg (egg-containing products such as cakes or biscuits) was not. The lowest risk for egg allergy was found in infants introduced to cooked egg at 4 to 6 months (OR: 0.2 [95% CI: 0.06–0.71]; P = .012). There was no association of egg allergy with duration of breastfeeding (after adjustment for family and personal history of allergy) or age of introduction of other solid foods.
Introduction of cooked egg (boiled, scrambled, fried, or poached) at 4 to 6 months of age might protect against egg allergy irrespective of family or personal history of allergy. Duration of breastfeeding and age of introduction of other solids does not seem to affect development of egg allergy.
In light of the changing perception that early instead of delayed exposure of commonly allergenic foods might lead to tolerance, this study is an important step in determining how the timing of introduction and form of food introduced (eg, cooked versus baked) might influence the development of food allergy. A large population was studied, and 75% of positive skin-prick-test results were confirmed with oral food challenges; however, egg-introduction history was retrospective and might have been subject to recall bias. The next step would be a prospective study on egg introduction to confirm these observations and to determine if the protective effect is limited only to egg or affects other food allergies such as those to peanut.
- Copyright © 2011 by the American Academy of Pediatrics