August 31, 2009

Milk safe, even encouraged for some kids after allergy treatment

Some children with a history of severe milk allergy can safely drink milk and consume other dairy products every day, according to research led by the Johns Hopkins Children’s Center and published in the Aug. 10 online edition of the Journal of Allergy and Clinical Immunology.

Investigators followed up with a subset of children who were part of an earlier Hopkins Children’s–led study published in 2008 in which patients allergic to milk were given increasingly higher doses of milk over time. For many of the children, continuous exposure to milk allergens—the proteins that trigger bad reactions—slowly and gradually retrained their immune systems to better tolerate the very food that once sent those systems into overdrive.

The follow-up of 18 children ages 6 to 16 whose severe milk allergies had eased or disappeared found that all of them were able to safely consume milk at home and that reactions, while common, were generally mild and grew milder over time. The follow-up period varied from three to 17 months, depending on how long it took patients to increase their milk intake.

These findings also suggest that regular use of milk and dairy foods may be needed for children to maintain their tolerance.

“We now have evidence from other studies that some children once successfully treated remain allergy-free even without daily exposure, while in others the allergies return once they stop regular daily exposure to milk,” said the study’s senior investigator, Robert Wood, a professor of pediatric immunology in the School of Medicine and director of Allergy and Immunology at Hopkins Children’s. “This may mean that some patients are truly cured of their allergy, while in others the immune system adapts to regular daily exposure to milk and may, in fact, need the exposure to continue to tolerate it,” he said.

After up to 17 months of at-home consumption, 13 of the 18 children who could tolerate increasingly higher doses of milk were asked to return to the clinic for tests. Of the 13, six showed no reaction after drinking 16,000 mg (16 ounces) of milk, twice the highest tolerated dose during the initial study, and seven had reactions at doses ranging from 3,000 mg to 16,000 mg. The reactions ranged from oral itch to hives, to sneezing, to mild abdominal pain, but none was serious. One child developed a cough requiring medications.

Investigators also continued to follow three children who could not tolerate doses higher than 2,540 mg (2.5 ounces)—the cutoff set by the investigators at the beginning of the follow-up—which made them ineligible to continue the at-home part of the study. All three continued to drink milk daily with minimal reactions, and two of them were eventually able to increase their consumption beyond 2,540 mg.

Sensitivity to milk was also measured with traditional skin prick testing, which showed gradual decreases in reactions over time. Seven children had no reactions at eight to 15 months of follow-up. Blood levels of milk IgE antibodies slowly decreased over time, too, another sign of better tolerance to milk. At the same time, a different type of antibody, IgG4—one that signals immunity to a particular allergen—went up over time, a marker of improved tolerance.

Children and their parents kept daily logs of milk and dairy consumption and recorded symptoms, such as hives, abdominal pain, sneezing and cough. During the first three months, consumption of milk triggered reactions 49 percent of the time, with some children experiencing as few as two reactions for every 100 doses of milk consumed. The figure dropped to 23 percent in the subsequent three months, and some children had no reactions at all.

Milk allergy is the most common type of food allergy and is experienced by 3 million children in the United States, according to the Centers for Disease Control and Prevention.

Co-investigators in the study are Satya Narisety, Robert Hamilton and Elizabeth Matsui, all of Johns Hopkins; Justin Skripak, of the Mt. Sinai School of Medicine; and Pamela Steele and A. Wesley Burks, both of Duke University.

The research was funded by the National Institutes of Health.

Wood receives funding support from Genentech, manufacturer of Xolair, a medication for the treatment of allergic asthma. He serves on the advisory board of the Food Allergy and Anaphylaxis Network.

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