Background: Cow's milk allergy (CMA) is the most common food allergy in infants and young children, affecting 2% to 3% of the general population. Most studies have shown the prognosis of developing tolerance to cow's milk to be good, with most outgrowing their allergy by age 3 years.
Objective: To define the natural course of CMA and identify the factors that best predict outcome in a large referral population of children with CMA.
Methods: Clinical history, test results, and final outcome were collected on 807 patients with IgE-mediated CMA. Patients were considered tolerant after they passed a challenge or experienced no reactions in the past 12 months and had a cow's milk IgE (cm-IgE) level <3 kU/L.
Results: Rates of resolution were 19% by age 4 years, 42% by age 8 years, 64% by age 12 years, and 79% by 16 years. Patients with persistent allergy had higher cm-IgE levels at all ages to age 16 years. The highest cm-IgE for each patient, defined as peak cm-IgE, was found to be highly predictive of outcome (P < .001). Coexisting asthma (P < .001) and allergic rhinitis (P < .001) were also significant predictors of outcome.
Conclusion: The prognosis for CMA in this population is worse than previously reported. However, some patients developed tolerance during adolescence, indicating that follow-up and re-evaluation of CMA patients is important in their care. cm-IgE level is highly predictive of outcome.
Clinical implications: The increasing potential for persistence of CMA, along with cm-IgE level's effect on prognosis, should be considered when counseling families regarding expected clinical course.