Commercial milk formula use in the first days of life increases allergy risk but small ongoing formula doses doesn't mitigate this
Bhasin et al 2025 study: summary
It's been observed previously that exposing the newborn to cow's milk formula in the first days of life is associated with an increased risk of developing peanut allergy, and theorised that this risk may be exacerbated because of the transient nature of the exposure.
Bhasin et al's study reframes this finding, suggesting that the problem may be less the formula exposure, and more that only partial exposure to the newborn's full biological requirement for colostrum increases the risk of food allergy to a range of proteins, beyond just considerations of cow's milk.
For this - and other - reasons, the theory that continuing small doses of formula as an allergy protective measure, once started, lacks credibility.
Methods
666 Australian term newborns who were either partially colostrum or fully colostrum fed in the first 3 days had an allergy prick test at 12-18 months of age. Allergy sensitisation on prick test was combined with maternal report of allergic reaction to make a diagnosis.
Findings
Up to half of the newborns received formula supplementation within the first 3 days, that is, during the colostrum feeding period. Early supplementation was associated with
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A five-fold increase in the risk of developing peanut allergy, which can be life-threatening and long-lasting.
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An 11-fold increase in the risk of developing more than one food allergy by 12–18 months. Importantly, the increased risk of peanut allergy was most pronounced in partial colostrum fed infants with later peanut allergen introduction, while it remained very low in exclusive colostrum fed (only breast milk fed) infants. This suggests that exclusive colostrum feeding is a primary preventive strategy, whereas early peanut introduction is a risk-mitigating strategy that might be especially relevant for the higher risk partial colostrum fed infants.
The authors write:
"Strikingly, we observed that nine or more colostrum feedings during the first 24 h of life might be protective against peanut allergy. These findings on the benefits of colostrum contrast with systematic reviews and meta-analyses indicating that breastfeeding's role in food allergy prevention is inconclusive. This suggests that colostrum, with its exceptionally rich composition of bioactive compounds, may be required to provide a critical foundation for healthy development as supported by preclinical and human studies."
With over a third of neonates globally only partially colostrum-fed, findings highlight the importance of promoting colostrum feeding and exploring colostrum-based therapies for high-risk infants.
Partial colostrum feeding (that is, formula supplementation) may be an overlooked risk factor for peanut and multiple food allergies.
Related resources
Infant allergy, unsettled behaviour, and the gut: PLAIN LANGUAGE SUMMARY for health professionals
Infant haematochezia (blood in the stool): PLAIN LANGUAGE SUMMARY for health professionals
Haematochezia and allergy in the breastfed infant. Dr Pamela Douglas 12 June 2024 - VIDEO
NDC clinical guidelines: Haematochezia and allergy in the breastfed infant POWERPOINT.pdf
For parents
It's normal for babies to have green stools and mucous in the stool
Is your baby unsettled or having trouble sleeping because of allergy?
Does allergy cause toddler sleep problems?
Infant cow's milk protein allergy (parent handout) available under possums.org Free Resources