Formula Modification and Clinical Outcomes in Infants with Atopic Dermatitis and Suspected Non–IgE–Mediated Cow’s Milk Protein Allergy: A Real-World Comparative Cohort Study

Background: Cow’s milk protein allergy (CMPA) is a common cause of gastrointestinal and dermatologic symptoms in infancy. In clinical practice, infants with atopic dermatitis (AD) and suspected non-IgE-mediated CMPA are frequently managed with formula modification, although real-world comparative data across different formula strategies remain limited. Aim: To evaluate gastrointestinal symptom resolution, improvement in AD, and growth outcomes following formula modification in infants with AD and suspected non-IgE-mediated CMPA. Methods: This retrospective comparative cohort study included 107 infants aged ≤12 months with documented AD and suspected non-IgE-mediated CMPA evaluated at a tertiary academic center between January 2024 and December 2025. Infants were categorized according to initial management strategy: switch to extensively hydrolyzed formula (eHF; n = 63), switch to amino acid formula (AAF; n = 29), or continued standard cow’s milk-based formula (n = 15). The primary outcome was resolution of gastrointestinal symptoms within 2–4 weeks. Secondary outcomes included improvement in AD, weight gain, and need for further formula escalation. Multivariable logistic regression was performed to adjust for potential confounders. Results: Overall, gastrointestinal symptom resolution occurred in 74 of 107 infants (69.2%). Resolution rates were 71.4% in the eHF group, 79.3% in the AAF group, and 40% in the standard formula group (p = 0.01). In adjusted analysis, switching to eHF (aOR 2.8; 95% CI 1.1–7.3; p = 0.03) and AAF (aOR 4.1; 95% CI 1.3–12.5; p = 0.01) was independently associated with higher odds of symptom resolution compared with continued standard formula. Improvement in AD was observed in 57.9% of infants overall and differed significantly across groups (p = 0.04). Mean weight gain during follow-up did not differ significantly between groups (p = 0.63). Subsequent formula escalation was more frequent in the standard formula group (46.7%) compared with eHF (17.5%) and AAF (13.8%) groups (p = 0.004). Conclusions: In infants with AD and suspected non-IgE-mediated CMPA, substitution with extensively hydrolyzed or amino acid formula was independently associated with greater gastrointestinal symptom resolution and improvement in dermatitis compared with continued standard formula, without evidence of compromised growth. These findings provide supportive real-world evidence consistent with current international guidelines; however, given the observational design and potential for residual confounding, they should be interpreted as hypothesis-generating rather than confirmatory evidence of causal treatment effects.