Early Introduction of Egg and the Development of Egg Allergy in Children: A Systematic Review and Meta-Analysis.

BACKGROUND: The timing of the introduction of egg to an infant's diet is of current interest, as new evidence raises questions regarding the benefit of delaying egg introduction. The objective of this study was to systematically review the existing literature regarding the effect of the early introduction of egg on the development of egg allergy. METHODS: Literature searches were conducted in MEDLINE, EMBASE, and CENTRAL, and trial protocols were searched in Meta Register and OpenGREY. Only randomized controlled trials (RCTs) comparing early (between 3 and 6 months of age) egg introduction to no early introduction were included. The primary outcome was the development of egg allergy. RESULTS: Of the 416 articles identified and screened, 6 RCTs met the eligibility criteria for data extraction. Allergic outcomes were evaluated in a total of 3,032 participants. A low to moderate level of evidence showed a benefit of the early introduction of egg (relative risk, RR 0.60, 95% CI 0.44-0.82, p = 0.002, mild heterogeneity, I2 = 23%). The absolute risk reduction for a population with an incidence of egg allergy of 9.3% was 37 fewer cases (95% CI 17-52) per 1,000 people. Consumption of < 4,000 mg/week of egg protein had a greater preventive effect than a higher dose. CONCLUSION: This systematic review and meta-analysis showed an association between the early introduction of egg and a lower risk of egg allergy. Furthermore, the nature and dose of egg protein exposure may play a role. These findings should be addressed in the context of primary studies.