16 March 2009

Exposure to peanuts ups tolerance

Exposing children with peanut allergies to a daily oral dose helped them build tolerance to the point where some of them appear to have lost their allergies, a new study found.


Exposing children with peanut allergies to a carefully administered daily oral dose of peanuts helped them build tolerance to the point where some of them appear to have lost their allergies, a new study found.

However, the researchers, from Duke University Medical Centre and Arkansas Children's Hospital, cautioned that the approach is still experimental and should not be tried by parents on their own.

"This is not something to be done at home," said Dr. Wesley Burks, chief of the division of paediatric allergy and immunology at Duke and a co-author of the research. "It truly is an investigational study."

But the children in the study did build long-term tolerance, with the researchers documenting key immunologic changes reflecting a lack of allergic response.

How the study was done
About four million Americans have allergies to foods, and tree nut allergies, including peanut allergies, are the most common. For the highly allergic, exposure to even a trace amount of peanuts can provoke a life-threatening reaction. Nearly half of the 150 deaths attributed to food allergies each year are caused by peanut allergies, according to background information in the study.

For the study, which began five years ago, Burks and his colleagues gave children with a history of peanut allergy gradually larger daily doses of peanut protein, while other allergic children were given a placebo. The starting doses were very small, as little as 1/1000th of a peanut. The doses increased until the children ate the equivalent of up to 15 peanuts a day about 10 months later, and then they stayed on the daily therapy while they were monitored.

Nine of the 33 children participating in the study have been on maintenance therapy for more than 2.5 years, and four of them were able to discontinue the treatment and eat peanuts, the researchers said.

When the researchers tracked immunologic changes - specifically levels of an antibody called immunoglobulin E, which the body makes in response to allergens - they found the levels had declined to nearly nothing at the end of the trial.

"I think what has been shown in this [research] is that the threshold [at which allergic reactions begin] really can change with treatment," Burks said.

Findings show promise
Changing the threshold is valuable, he said, because it could mean that if a child with a peanut allergy accidentally ate something with peanut in it, he may have no reaction. "If you do that alone, you give the family comfort," he said.

Still to be answered is whether doctors can "make the disease go away", Burks said, adding that his research will continue. The concept of exposing an allergic person to small amounts of the allergen isn't new, of course, said Dr Scott Sicherer, associate professor of paediatrics and chief of the division of paediatric allergy and immunology at Mount Sinai School of Medicine in New York City.

That's the idea behind allergy shots. "I think this [Duke-Arkansas] is very promising, the results", added Sicherer, who's also chairman of the American Academy of Paediatrics' Section on Allergy and Immunology.

Funding for the study was provided by the US National Institutes of Health, the Food Allergy and Anaphylaxis Network, the Food Allergy Project, the Gerber Foundation and the Robins Family Foundation. – (HealthDay News, March 2009)

Read more:
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