Granted, I didn't need a special study to understand that milk allergies are not always outgrown during infancy.  My milk allergy has twisted and turned through various symptoms, yet it has persisted into adulthood.  However, it seems that I am further from alone than once thought.  While prior estimates had stated that roughly 80% of milk allergies are outgrown by the age of 6, a new study out of the Johns Hopkins University School of Medicine in Baltimore, Maryland claims that these numbers are far too optimistic.  Rates of milk allergy resolution were found to be 19% by age 4 years, 42% by age 8 years, 64% by age 12 years, and 79% by 16 years.

The following was detailed in the 2007 report, “The natural history of IgE-mediated cow's milk allergy” in the Journal of Allergy and Clinical Immunology:

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.