Early Discontinuation of Cow's Milk Protein Ingestion Is Associated with the Development of Cow's Milk Allergy

BACKGROUND: Although early supplementation with cow's milk formula (CMF) reportedly increases the risk of cow's milk allergy (CMA) in breast-fed infants, little is known about the association between the timing of CMF discontinuation and subsequent CMA development. OBJECTIVE: To elucidate the relationship between the timing of CMF discontinuation and CMA development in infants who received CMF in the early days of life. METHODS: Using data from a randomized controlled trial of birth cohort from 4 Japanese hospitals, we performed a subgroup analysis of participants who ingested CMF in the first 3 days of life. We compared the proportions of participants who developed CMA at age 6 months in those who discontinued CMF ingestion before age 1 month ("DISC <1-month group"), during age 1 to 2 months ("DISC 1-2 -month group"), and during age 3 to 5 months ("DISC 3-5 -month group") with those who continued CMF ingestion until age 6 months ("continuous group"). The risk ratios (RRs) and 95% CIs for CMA development were calculated. RESULTS: CMA incidence was significantly higher in the DISC <1-month group (n = 7 of 17, 41.2%; RR, 65.7; 95% CI, 14.7292.5; P < .001), DISC 1-2 -month group (n = 3 of 26, 11.5%; RR, 18.4; 95% CI, 3.2-105.3; P = .003), and DISC 3-5 -month group (n = 7 of 69, 10.1%; RR, 16.2; 95% CI, 3.4-76.2; P < .001) than in the continuous group (n = 2 of 319, 0.6%). CONCLUSIONS: Early CMF discontinuation, particularly in the first month of life, was associated with CMA development in infants who received CMF in the first 3 days of life. (c) 2021 American Academy of Allergy, Asthma & Immunology