Does cow's milk formula cause more frequent food allergies in newborns at increased risk of atopy?

In infants at increased risk of atopy, restricting cow's milk supplementation for the first 3 days of life is associated with a significantly lower risk of developing a cow's milk allergy and food allergies by 24 months of age. (LOE = 2b)

Urashima M, Mezawa H, Okuyama M, et al. Primary prevention of cow's milk sensitization and food allergy by avoiding supplementation with cow's milk formula at birth: a randomized clinical trial. JAMA Pediatr 2019;173(12):1137-1145.  [PMID:31633778]

Randomized controlled trial (nonblinded)

Government

Concealed

Inpatient (any location) with outpatient follow-up

This study, which took place at a university hospital in Japan, included breastfed newborns at increased risk of atopy (ie, having a father, mother, or siblings with current or past atopic diseases such as asthma). The newborns were randomized to receive supplementation (if desired) with an amino acid-based elemental formula for at least the first 3 days of life (n = 156) or with cow's milk formula (n = 156) from the first day of life. When the infants were 24 months of age, the researchers evaluated serum levels of IgE in response to cow's milk and other specific foods using intention-to-treat analysis. They had follow-up data on all but 10 of the children. At 24 months of age, 17% of infants initially restricted from cow's milk developed elevated IgE to cow's milk compared with 32% of the control infants (number needed to treat = 7; 95% CI 5 - 21). Clinical food allergies (2.6% vs 13.2%; number needed to treat [NNT] = 10; 6 - 23) and anaphylaxis (0.7% vs 8.6%; NNT = 13; 8 - 31) were less frequent in the infants initially restricted from cow's milk supplements. The rate of anaphylaxis in the control infants seems much higher than I would have expected. The study's applicability to other populations may be limited. Nonetheless, restricting cow's milk supplementation for the first 3 days of life is a relatively simple and inexpensive intervention!