Cow's milk allergy persists longer than previously reported, and the majority of children may retain the sensitivity into school age, study findings suggest.

"The old data saying that most milk allergy will be easily outgrown, usually by the age of 3 years, is most likely wrong," Dr Robert A. Wood, at Johns Hopkins University School of Medicine, told Reuters Health.

He and colleagues found that just 19 percent of children allergic to cow's milk outgrew their allergy by age 4.

Moreover, Wood added, "some children will outgrow their allergy into their teenage years, which was previously thought to be unlikely." His team found that by the ages of 8, 12, and 16 years, 42 percent, 64 percent, and 79 percent, respectively, had outgrown their milk allergy.

Wood and colleagues reviewed the clinical history of 807 children who were treated at a pediatric allergy clinic for milk allergy. Children were considered to have acquired tolerance if they passed a skin prick test, reported drinking milk without a reaction for the last years and had cow's milk associated immunoglobulin E antibody levels less than 3 kU/L.

"The higher the level of immunoglobulin-E antibody, the stronger the allergy," Wood said. "Therefore, higher levels not only confirm the allergy but make it less likely that the allergy will be outgrown, or at least that it will take longer to outgrow," he added.

They also found that children with asthma and allergic rhinitis had a decreased likelihood of developing tolerance to milk products.

In this population of highly allergic children, 91 percent had at least one other food allergy, most commonly to eggs and peanut.

The most common symptom of milk allergy was skin-related reactions, affecting 85 percent, followed by vomiting, diarrhea or another gastrointestinal reaction in 46 percent; wheezing, cough or difficulty breathing occurred in14 percent; and nasal congestion or other upper respiratory symptoms were seen in 6 percent, the investigators note in the Journal of Allergy and Clinical Immunology.

Wood and colleagues suggest their findings be corroborated through similar studies in a more general population of children with milk allergies. - Reuters