Background. Cow’s milk allergy (CMA) is the most common food allergy in early childhood. Children with CMA require a precise and punctual diagnosis. Oral food challenge (OFC) is the gold-standard procedure for diagnosing allergies, but it is laborious and requires a particular setting. The aim of the study was to identify the cutoff value of serum allergen-specific IgE values able to predict a positive response to OFC. Methods. Children with suspected CMA performed OFC with cow’s milk (CM) or derivatives. Total IgE and specific IgE to raw CM, α-lactalbumin, β-lactoglobulin, and casein were measured. Results. Seventy-two children performed OFC, and 30 (41.6%) had a positive response. The significant predictive factors were sensitization to raw CM extract ( p = 0.03 ), α-lactalbumin ( p = 0.013 ), β-lactoglobulin ( p = 0.09 ), and casein ( p = 0.019 ). The cutoff was, respectively: 5.13 kUA/L for raw CM, 1.47 for α-lactalbumin, 1.35 for β-lactoglobulin, and 4.87 for casein. Conclusions. This study allowed us to define a set of cutoff values for CM protein-specific IgE. However, these cutoffs should be interpreted not as a diagnostic tool for CMA but only predictive of response to OFC in a specific territory. Thus, the practical message may be that a value above the cutoff allows a good approximation to identify children to be started on OFC.