Early, continuing exposure to cow's milk formula and cow's milk allergy The COMEET study, a single center, prospective interventional study

Background: Cow's milk allergy (CMA) is a common food allergy among infants. Information regarding the best timing for first exposure to cow's milk formula (CMF) is controversial and more evidence is required. Few ran-domized control trials have tried to accurately assess the timing and preventive effect of exposure to CMF on small cohorts.Objective: This study assessed the association between early, continuing exposure to CMF on the basis of the parents' preferences and the development of immunoglobulin E (IgE)-mediated CMA in a large birth cohort.Methods: Newborns were prospectively recruited shortly before birth and divided into 2 groups according to parental feeding preference for the first 2 months of life: (1) exclusive breastfeeding (EBF); or (2) at least 1 meal of CMF (with or without breastfeeding) daily. Infants were followed up monthly until the age of 12 months. Results: Among 1992 infants participating in the study, 1073 (53.86%) were in the EBF group until 2 months of age. IgE-mediated CMA was confirmed in 0.85% (n = 17); all were in the EBF group. Within this group, the preva-lence of IgE-mediated CMA was 1.58% compared with 0 in the other groups (relative risk, 29.98; P < .001). Post hoc analysis revealed IgE-mediated CMA prevalence of 0.7% in the per-protocol EBF group vs 3.27% among breastfed infants who were exposed to a small amount of CMF during the first 2 months of life. A family atopic background did not affect the results. Conclusion: Early, continuing exposure to CMF from birth has the potential to prevent the development of IgE-mediated CMA and should be encouraged. However, the exposure needs to be consistent because occasional exposure increases the risk of developing IgE-mediated CMA and should be avoided.(c) 2022 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.