TOPLINE:

Exposure to cow’s milk formula (CMF) in the first week of life (ie, very early transient exposure) was not associated with an increased risk for cow’s milk allergy or sensitization at the age of 1 year, and cow’s milk-related atopic outcomes were uncommon by the age of 6 years.

METHODOLOGY:

• Researchers analyzed data from 940 children (48.1% girls) from the HealthNuts study to assess whether the timing of exposure to CMF during the first 3 months of life, including the first week, altered the risk for cow’s milk sensitization or allergy by the age of 6 years.
• CMF included standard and partially hydrolyzed formulas as well as lactose-free or reflux/colic formulas, and infants exposed only to extensively hydrolyzed or amino acid-based formulas were categorized as not exposed to CMF.
• Exposure to CMF was categorized as no exposure during the first 3 months of life, very early transient exposure (exposure only in the first week), very early persistent exposure (exposure during and after the first week), and early exposure (exposure after the first week through 3 months of age).
• Sensitization to cow’s milk was defined as obtaining a wheal size ≥ 2 mm on a skin prick test at the age of 1 year or a wheal size ≥ 3 mm at the age of 6 years; cow’s milk allergy was defined as sensitization plus a parent-reported reaction to cow’s milk at the age of 1 year or a positive oral food challenge and sensitization at the age of 6 years.

TAKEAWAY:

• Overall, 46.9% of children received CMF during the first 3 months of life: 20.2% started receiving it in the first week and continued thereafter, 12.7% had transient exposure in the first week only, and 14.0% started receiving it after the first week.
• Very early transient exposure to CMF was not associated with the risk for cow’s milk allergy (adjusted odds ratio [aOR], 1.27; P = .823) or sensitization (aOR, 2.23; P = .144) at the age of 1 year.
• At the age of 6 years, the prevalence of cow’s milk allergy and sensitization was low (0.1% and 0.5%, respectively). All cases occurred in children who did not receive CMF during the first 3 months.
• Parent-reported reactions to cow’s milk at the age of 1 year were not associated with reduced odds of early or very early persistent exposure to CMF compared with no exposure (aOR, 0.22; P = .138 and aOR, 0.29; P = .097, respectively).

IN PRACTICE:

“Cow’s milk atopic outcomes are uncommon at age 6 as the majority of children are outgrowing their allergy, regardless of when they are exposed to cow’s milk formula in early life,” the authors wrote. “These potential impacts on food allergy outcomes should be interpreted with caution, as very early and persistent cow’s milk exposure may have a range of detrimental impacts on the child’s health, including the establishment and duration of breastfeeding, which is linked to a range of benefits for the child and mother,” they added.

SOURCE:

Jennifer Koplin, PhD, with The University of Queensland, Brisbane, Australia, was the corresponding author of the study, which was published online on April 15, 2026, in The Journal of Allergy and Clinical Immunology: In Practice.

LIMITATIONS:

The study was limited by its reliance on data regarding formula feeding in hospitals from the Victorian Perinatal Data Collection system and by the lack of information on the type of formula and on the outcomes of oral food challenges to cow’s milk at the age of 1 year.

DISCLOSURES:

The HealthNuts study was supported by funding from the National Health and Medical Research Council of Australia, Ilhan Food Allergy Foundation, AnaphylaxiStop, The Sylvia and Charles Viertel Charitable Foundation, and the Victorian Government’s Operational Infrastructure Support Program. Some authors reported receiving research grants, fellowships, consultant and speaker fees, speaker honoraria, and prizes paid to institutions and having roles in advisory panel consultancy with various pharmaceutical companies and institutions. One author also reported receiving an investigational product free of charge.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.