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Early and ongoing infant cow’s milk exposure may prevent allergy

Published: June 29, 2022

Cow’s milk allergy is among the most common food allergies in young children, and cow’s milk protein is often introduced before any other allergens or foods, in the form of milk-based infant formulas. In fact, many infants receive formula within hours of birth. Recent research on peanut allergy has led to new allergy prevention paradigms supporting the early introduction of peanuts, along with other complementary foods, at 4-6 months of age. However, it is not known whether the idea of “earlier is better” also applies to cow’s milk. Other recent studies have explored the relationship between timing of early exposure to cow’s milk and later milk allergy symptoms. This study was unique in that the investigators also had data on formula supplementation in the hospital after birth, in addition to information about babies’ intake of infant formula and other cow’s milk-based products across infancy. This allowed them to explore the interaction between the timing of infant milk exposures in a novel way.

In a study published in The Journal of Allergy and Clinical Immunology: In Practice, Switkowski et al. used data from approximately 1,300 children participating in the Boston-area Project Viva study, which follows a group of mothers and their children born in 1999-2002. The team examined the timing of cow’s milk protein introduction, either from milk-based formula or other cow’s milk products. They categorized milk protein introduction as occurring within 2 weeks of birth, between 2 weeks and 6 months of age, or after 6 months, and studied these time periods in relation to adverse reactions to cow’s milk reported by parents later in childhood. These researchers were also able to assess whether the relationship between timing of cow’s milk introduction and later adverse reactions to cow’s milk depended on whether the infant had received any formula shortly after birth.
Overall, infants who were first introduced to cow’s milk at or after 6 months of age had the highest risk for later adverse reactions to cow’s milk. Importantly, the relationship between timing of milk introduction and later adverse reactions was different for babies who were given formula in the hospital in the few days after birth and those who were not. Babies who did get formula in the hospital just after birth had the lowest risk of developing adverse reactions to cow’s milk, but only if they continued to receive a cow’s milk-based formula within the 2 weeks after birth. Among babies who didn’t get any formula just after birth, the best time to introduce cow’s milk protein seemed to be later – sometime between 2 weeks and 6 months. The findings support not delaying introduction of cow’s milk protein beyond 6 months and suggest that earlier introduction may be even better. Additionally, supplemental formula immediately after birth may potentially increase the risk of milk allergy among babies who go on to be exclusively breastfed after they leave the hospital, but this risk may be less in babies who continue to get some formula and some breastmilk during the first two weeks of life.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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