Early exposure to cow's milk protein is protective against IgE-mediated cow's milk protein allergy.

BACKGROUND The diversity in the perceived prevalence, recovery, and risk factors for cow's milk allergy (CMA) necessitated a large-scale, population-based prospective study. OBJECTIVE We sought to determine the prevalence, cross-reactivity with soy allergy, and risk factors for the development of CMA. METHODS In a prospective study the feeding history of 13,019 infants was obtained by means of telephone interview (95.8%) or questionnaire (4.2%). Infants with probable adverse reactions to milk were examined, skin prick tested, and challenged orally. RESULTS Ninety-eight percent of the cohort participated in the study. The cumulative incidence for IgE-mediated CMA was 0.5% (66/13,019 patients). The mean age of cow's milk protein (CMP) introduction was significantly different (P < .001) between the healthy infants (61.6 +/- 92.5 days) and those with IgE-mediated CMA (116.1 +/- 64.9 days). Only 0.05% of the infants who were started on regular CMP formula within the first 14 days versus 1.75% who were started on formula between the ages of 105 and 194 days had IgE-mediated CMA (P < .001). The odds ratio was 19.3 (95% CI, 6.0-62.1) for development of IgE-mediated CMA among infants with exposure to CMP at the age of 15 days or more (P < .001). Sixty-four patients with IgE-mediated CMA tolerated soy, and none had a proved allergy to soy. CONCLUSIONS IgE-mediated CMA is much less common than generally reported. Early exposure to CMP as a supplement to breast-feeding might promote tolerance. Finally, soy is a reasonable feeding alternative in patients with IgE-mediated CMA.