SATURDAY, March 19 (HealthDay News) -- Children may not be outgrowing their allergy to milk as quickly as experts previously have believed.
In a study of 244 children with confirmed milk allergy, just over a third outgrew it within 30 months.
But that finding is in conflict with earlier studies that found a much higher percentage of children outgrowing the allergy fairly quickly, said Dr. Scott Sicherer, a pediatrics professor at the Mount Sinai School of Medicine in New York City, who led the new research.
"We used to say 85 or 90 percent would outgrow [milk allergies] by the time they are 3 or 4 years old," Sicherer said. But more recent studies, he said, are finding that children may be hanging on to the allergy longer.
Sicherer was to present the new study's findings Saturday in San Francisco at the annual meeting of the American Academy of Allergy, Asthma & Immunology.
About 2.5 percent of children younger than 3 years are allergic to milk, according to the Food Allergy & Anaphylaxis Network. The allergy typically appears during the first year of life.
Milk allergy involves an immune system response in which antibodies react to the offensive milk proteins. It's different, Sicherer said, from the much more common lactose intolerance, in which a deficiency in the enzyme lactase makes it difficult to digest lactose, a sugar found in milk.
For their research, which included another study as well, Sicherer and his colleagues enrolled more than 500 children, 3 to 15 months old, to evaluate egg and milk allergies. The study presented at the meeting focused just on those with milk allergy.
In all, 244 children were found to be allergic to milk, verified either by a blood test that measures antibodies known as IgE (which can react to the milk proteins casein or whey), medical history of an allergy, a positive skin test or a skin rash after drinking milk.
At the end of the 30-month follow-up, 36.9 percent had outgrown the allergy. The researchers determined the allergy had resolved when the child could successfully drink milk without a reaction.
Certain factors predicted which children would outgrow it, Sicherer said. Children with a lower concentration of the IgE antibodies in the blood test were more likely to outgrow the allergy, he said, as were those who had less severe dermatitis and those who had a mild reaction to the skin test.
Although the percent of youngsters who outgrew the allergy to milk fairly quickly is lower than previously thought, Sicherer said, there is always hope.
"You can outgrow an allergy at any age," he said. "More than 85 percent of kids eventually outgrow" a milk allergy.
The study was funded by the Consortium of Food Allergy Research, established through a U.S. National Institutes of Health grant.
Dr. Jeffrey M. Factor, an allergist in West Hartford, Conn., who is on staff at Connecticut Children's Medical Center in Hartford and is an associate clinical professor of pediatrics at the University of Connecticut School of Medicine, said that the study findings are no surprise as they reflect clinical practice.
"Some other recent studies over the past four or five years or thereabouts have suggested that children are not outgrowing milk allergy as early as has been previously believed," Factor said. He reviewed the study findings but was not involved in the research.
"Most do eventually outgrow milk allergy, but it seems that many of them are outgrowing milk allergy in later childhood, even into the second decade of life," said Factor, who has been in practice for about 20 years.
Exactly why is not known. "Food allergies are becoming more prevalent in general for reasons not clear, and they are becoming more severe," he said.
The new study findings may serve as a message to parents not to expect their child to outgrow the milk allergy by the time the child starts school, as has been suggested. "I think it's important not to provide overly optimistic numbers to parents that their child is going to outgrow their milk allergy absolutely by grade school," Factor said.
Milk allergy symptoms typically appear soon after a child drinks milk, even within minutes, Sicherer said. These can include skin rashes that look similar to a mosquito bite, itchy red rashes, vomiting and wheezing.
The study findings should be considered preliminary because they were to be presented at a medical meeting and have not been subjected to the same type of scrutiny given research published in medical journals.
The Food Allergy & Anaphylaxis Network has more about milk allergy.
SOURCE: Scott Sicherer, M.D., professor, pediatrics, Mount Sinai School of Medicine, New York City; Jeffrey M. Factor, M.D., allergist, Connecticut Children's Medical Center, Hartford, Conn., and associate clinical professor of pediatrics, University of Connecticut School of Medicine, Farmington; presentation, American Academy of Allergy, Asthma & Immunology annual meeting, March 18, 2011, San Francisco
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