Milk allergies harder to outgrow the previously thought.

New research from scientists at the John Hopkins Children's Center has found that milk allergies in children may be much more persistent and harder to outgrow than was previously believed. The study, of 800 children with milk allergy, found that only one-fifth of children outgrew their allergy to milk by age four, while only 42% outgrew it by age eight. 79% were allergy-free by age 16. Earlier research had suggested that three-quarters of children who are allergic to milk outgrew the allergy by age three.

"The bad news is that the prognosis for a child with a milk or egg allergy appears to be worse than it was 20 years ago," said lead researcher Robert Wood, head of allergy and immunology at John Hopkin's Children's Center. "Not only do more kids have allergies, but fewer of them outgrow their allergies, and those who do, do so later than before."

Food allergies diagnosed recently seem to behave more unpredictably and more aggressively than those diagnosed in the past, Wood said. "We may be dealing with a different kind of disease process than we did 20 years ago. Why this is happening we just don't know." One positive finding of the study was that some children lost their allergies during adolescence, which had not previously been thought possible.

Milk allergy is one of the most common food allergies in the United States, affecting 3% of children.