Current guidelines emphasize early introduction to potentially allergenic foods, but the optimal timing, amount and exposure routes for foods other than peanut are not well-established. Cow's milk is often the first allergenic food introduced through infant formulas.
We examined timing of cow's milk protein introduction (CMPI), including interaction with formula supplementation after delivery, in relation to reported cow's milk adverse reactions (CMARs), throughout childhood.
Among children in the Boston, MA-area Project Viva cohort, we assessed timing of CMPI (<2wks, 2wks-<6mos, ≥6mos) with questionnaires administered in infancy. Outcomes were: 1) parent-reported CMAR via annual questionnaires from 2-13yrs (n=1298); and 2) milk sensitization (n=505) and IgE-mediated milk allergy (n=491) at ∼8yrs. We used multivariable logistic regression models adjusted for parental atopy history, delivery mode, gestational age at delivery, child race and census tract median household income, and investigated effect modification by ever/never breastfed status and formula supplementation in the delivery hospital.
32% were introduced to cow's milk protein at <2wks, 38% at 2wks-<6mos, and 30% at ≥6mos. Compared to children with CMPI <2wks, children with CMPI ≥6mos had higher risk of CMAR at 2-5yrs (OR: 2.4 [1.2, 4.7]). Children given formula after delivery + CMPI <2wks had the lowest risk overall. Among children not given formula after delivery, CMPI 2wks-6mos appeared most protective. Results were similar among ever-breastfed children. Timing of CMPI was not associated with milk sensitization or IgE-mediated milk allergy in mid-childhood.
Early, consistent cow's milk exposure appears protective against adverse reactions to cow's milk.