Early Exposure to Cow's Milk Protein Is Associated with a Reduced Risk of Cow's Milk Allergic Outcomes.

BACKGROUND

Overall early exposure to allergenic foods in the infant's diet is a new strategy for preventing food allergy to that allergen, but the optimal timing of exposure for different allergens is not known.

OBJECTIVES

We aimed to examine the relationship between exposure to cow's milk protein in the first 3 months of life and risk of cow's milk allergy at age 12 months.

METHODS

HealthNuts is a longitudinal population-based food allergy study that recruited 5,276 twelve-month-old infants. Skin prick testing to cow's milk was conducted on the second half of the cohort (n = 2,715) and sensitization defined as a wheal ≥2 mm. Cow's milk allergy was defined as a parent-reported reaction to cow's milk consistent with IgE-mediated allergy together with evidence of sensitization. Early exposure to cow's milk protein was captured through parental questionnaire administered at 1 year of age and defined as consumption of cow's milk-based infant formula during the first 3 months of life.

RESULTS

Forty-two percent of infants were exposed to cow's milk in the first 3 months of life (n= 1,977/4,712) and 87% of these infants were also breastfed. Early exposure to cow's milk protein was associated with a reduced risk of cow's milk sensitization (adjusted odds ratio [aOR] 0.44, 95% confidence interval [CI] 0.23-0.83), parent-reported reactions to cow's milk (aOR 0.44, 95% CI 0.29-0.67), and cow's milk allergy (aOR 0.31, 95% CI 0.10-0.91) at age 12 months. Age at exposure to cow's milk protein was not associated with the risk of other food allergies.

CONCLUSIONS

Exposure to cow's milk protein in the first 3 months of life was associated with a reduced risk of cow's milk allergy. These findings are from an observational study and clinical trials are warranted to further assess this association before any recommendations to infant feeding guidelines can be made.