Background: Many infants are sensitized to chicken eggs before the introduction of complementary food. However, the route of sensitization to chicken eggs remains unclear. Objective: To investigate the mechanism of sensitization to chicken eggs in infants. Methods: This birth cohort study included 131 unselected infants who underwent physical examination and the skin prick test every 3 months until 1 year of age. Parents completed a questionnaire at each visit, and maternal consumption of chicken eggs during the previous month was reported at 0, 1, and 6 months after delivery. Results: Of 131 infants, 33 (25%) were sensitized to egg white at 6 months. The sensitization rate increased with an increase in maternal egg consumption, whereas the rate was substantially lower when the mother had consumed a larger amount during late pregnancy or at 1 month. Comparison of infants of mothers with similar egg consumption levels revealed a higher incidence of sensitization or food allergy (FA) in infants who consumed more breast milk. Conclusion: Maternal egg consumption may modulate the sensitization status depending on the timing or amount of eggs consumed. Oral tolerance could be influenced by maternal consumption only until early infancy. Egg-white antigen in breast milk had a stronger association with sensitization or FA development than environmental antigens.