Predicting Oral Food Challenge Outcomes in Cow’s Milk Protein Allergy: The Crucial Role of Bos d 8 and Component-Resolved Diagnostics: A Narrative Review

Approximately 1–2% of infants have cow’s milk protein allergy (CMPA). From a clinical perspective, diagnosing CMPA using the oral food challenge (OFC) is high risk, necessitating safer alternatives. One possible alternative is component-resolved diagnostics (CRD). This narrative review examines specific IgE (sIgE) thresholds for cow’s milk protein in predicting outcomes of OFCs in European children. Eligible studies focusing on CRD in European pediatric populations were identified through PubMed and Scopus databases. Our findings highlight the crucial role of Bos d 8 (casein) in the diagnostic process. Among the analyzed milk components, Bos d 8 appeared to be a promising marker for predicting positive OFC outcomes in several cohorts. However, due to significant population heterogeneity, conflicting findings exist, with some studies indicating that no single molecular component is consistently superior to whole cow’s milk specific IgE. While other molecules, such as Bos d 6 and lactoferrin, showed limited diagnostic utility, specific IgE to Bos d 8 demonstrated the highest clinical value. Although the double-blind, placebo-controlled food challenge (DBPCFC) remains the gold standard for CMPA diagnosis, the use of Bos d 8 in CRD is a key step toward risk stratification and may help reduce the need for high-risk OFCs in selected patients.