A recent systematic review indicates that food sensitization in early childhood is a risk factor, not only for food allergies, but also for developing an allergic march which can lead to airway allergic diseases. 1 Over the past few decades, many groups have studied risk factors for allergic diseases, including sensitization. These risks include eczema, gut microbiome, timing of introduction of solid food, vitamin D, etc. Among these, eczema is thought to be one of the most important factors for food sensitization and developing food allergy. 2,3 However, the prophylactic use of emollients could not prevent food allergen sensitization in infants even if it decreases eczema prevalence, 4 indicating that other factors are involved. The WHO recommends exclusive breastfeeding for at least 6 months in all infants. However, the possible effects of breastfeeding on childhood allergic sensitization and allergic diseases are controversial. 5This study aimed to analyze the risk factors producing hen's egg sensitization at the age of 1 year, including feeding methods, in a highrisk birth cohort in Chiba, an urban area near Tokyo.A birth cohort study of newborn infants with a family history of allergies was jointly arranged in the Seikei-kai Chiba Medical Center and the Chiba University Hospital from January 2010 to December 2011. The study protocols were approved by the Bioethics Review Committee, Faculty of Medicine, Chiba University, Japan (approval no. 754). Informed consent was obtained from each study subject's guardian. After the study subjects' births, we reconfirmed their eligibility. We asked the guardians to take the study subjects to their designated clinic at 1 month, 6 months, and 1 year of age to take physical examinations. Other details of this study are shown in Appendix S1. The detailed schedule of this CHIBA study is shown in breastmilk might be important for sensitization. In addition, breastmilk contains only minimal amounts of vitamin D, which is thought to have a protective effect against allergic diseases. 8There are some limitations in our study. Since we used a highrisk cohort, it is not clear that we can generalize our results to the normal population. However, we think that it is important to prevent allergic diseases from affecting high-risk groups. As mentioned above, we could not determine the exact amount of EW intake from infant foods to check the effect of early intake of hen's egg. However, the timing of the introduction of infant foods did not affect the EW sensitization in the present study (data not shown).In conclusion, although the effects of breastmilk on allergic diseases remain controversial, our results showed that breastfeeding is a risk factor for egg white sensitization. Immune components in the breastmilk might affect the sensitization at 1 year of age. However, the mechanism through which breastmilk induces allergic sensitization is currently unknown. We are planning to investigate the breastmilk components that might affect allergic sensitization.
ACK N OWLED G M ENTSWe than...