Background: Cow's milk allergy is the most prevalent food hypersensitivity, affecting 2–3% of infants, but it tends to resolve with age. Cow’s milk-specific immunoglobulin E in the serum is an important measure in the diagnosis and follow-up of infants and children with cow's milk allergy.

Objectives: To examine the relation between CmsIgE[1] and the probability of resolution of milk allergy.

Methods: CMsIgE was determined in the serum of 1800 infants and children referred for the evaluation of possible milk allergy. All children with CmsIgE of 1 kU/L or above were followed at the allergy clinic and, according to their condition, underwent milk challenge. The diagnosis of cow's milk allergy was made on the basis of a significant and specific history or a positive oral food challenge. Subsequently, oral tolerance was defined as an uneventful oral challenge.

Results: A total of 135 infants and children had milk-specific IgE greater than 1 kU/L. Forty-one percent of children still had clinical milk allergy after the age of 3 years. Sixty-eight percent of children older than 3 years with persistence of cow's milk allergy had milk-specific IgE > 3 IU/ml before the age of 1 year. Furthermore, 70% of children who at 3 years old had resolved their cow's milk allergy had milk-specific IgE that was lower than 3 IU/ml before the age of 1 year. The positive predictive value of CmsIgE > 3 IU/ml to persistent cow's milk allergy at age 3 years was 82.6% (P = 0.001), with a sensitivity of 67.9% and specificity of 70.4%.

Conclusions: Milk-specific IgE concentration in the first year of life can serve as a predictor of the persistence of milk allergy.