Short-term early exposure to cow's milk formula increases the risk of cow's milk allergy: A critical window in early life.

OBJECTIVE

To determine whether the timing and continuity of neonatal cow's milk formula (CMF) exposure influence the risk of IgE-mediated cow's milk protein allergy (CMPA).

METHODS

This retrospective case-control study included 376 children (182 with CMPA and 194 healthy controls). Early feeding patterns-including timing of CMF initiation and duration of exposure-were evaluated. Multivariable logistic regression analyses were performed to assess independent risk factors while adjusting for potential confounders.

RESULTS

Among infants exposed to cow's milk formula within the first 72 h, discontinuation within 14 days was associated with higher odds of CMPA than continued exposure for ≥15 days (aOR: 8.07; 95% CI: 3.20-20.36; p < .001). In contrast, continuous exposure (≥15 days) was associated with substantially lower odds of CMPA, independent of delivery mode.

CONCLUSION

Not early exposure per se, but brief and discontinuous exposure appears to drive sensitization. These findings highlight a critical "window of vulnerability" in early life, suggesting that unnecessary short-term formula supplementation should be avoided, while continuous exposure-if initiated-may support oral tolerance development and may have immediate implications for neonatal feeding practices and allergy prevention strategies.