Oral Immunotherapy May Desensitize Allergic Children; Skin Test May Predict Who Will Outgrow
By Kathleen Doheny
WebMD Health News
Latest Allergies News
Reviewed By Louise Chang, MD
on Monday, February 26, 2007
Small doses of peanut protein, given for months under medical supervision, can desensitize children with peanut allergy, reducing the risk of a reaction if they accidentally eat peanuts, according to a new study.
In other new research, scientists say they have found a way to predict which children are likely to outgrow their allergy to peanuts.
Both studies were presented Saturday at the 2007 Annual Meeting of the American Academy of Allergy, Asthma and Immunology in San Diego.
About Peanut Allergies
Peanut allergies affect about 1% of the U.S. population, according to the Academy.
Reactions can range from mild to severe, even leading to anaphylaxis, a potentially fatal response that can cause breathing problems and loss of consciousness.
Traditional advice for food allergies was to simply avoid the food.
But avoiding all peanut-containing foods can be difficult and accidental ingestion often occurs, says Scott David Nash, MD, allergy fellow at Duke University and an author of the desensitization study.
With immunotherapy, tiny amounts of the allergens are injected until tolerance develops.
Oral Peanut Immunotherapy
So Nash's team decided to try oral immunotherapy for peanut allergy problems, giving eight children with known peanut allergy escalating doses of peanut protein in the form of a flour mixed into applesauce or other food.
"We are the first to do a trial of oral immunotherapy for peanut allergy," he tells WebMD.
The treatment included three phases: one day in the medical center, with increasing doses given throughout the day; a home phase lasting three or four months that involved daily, escalating doses; and a home maintenance phase in which the daily dose was 300 milligrams, about the equivalent of one peanut.
The maintenance phase lasted up to 18 months, depending on how much peanut protein the child tolerated.
At the end of the study, which seven children completed, Nash's team gave the children a "food challenge" to peanut flour, exposing them to up to nearly 8 grams, or the equivalent of more than 13 peanuts.
"Most [five of seven] tolerated the equivalent of 13 peanuts at the food challenge at the end of the study," Nash says.
Immune system changes from the start to the end of the study showed growing tolerance to the peanut protein, he says.
Goals of Immunotherapy
"What we would like to have happen is for their food allergy to go away," Nash says.
For now, however, he says, "We have essentially proven they can tolerate an accidental ingestion. We think our patients now are at reduced risk for anaphylaxis."
Egg Allergies Studied
"No one should try this at home," Nash cautions. The concept is still in the research phases, and Nash says it's difficult to say when allergists might begin adopting the practice.
Parents in the study were told to contact the center if they suspected reactions; most reactions occurred in the clinic, not at home, Nash says.
More research is needed, he says, to prove the concept safe and effective.
Similar research is being done with egg immunotherapy. Wesley Burks, MD, another author of the peanut immunotherapy study, has done a similar study on egg allergies, Nash says.
The Remission Question
When parents find out their child is allergic to peanuts, they always ask the same question, says Katie Allen, MD, PhD: "Are they going to be one of the 20% who grow out of it?"
Allen is a pediatric gastroenterologist and allergist at the Murdoch Children's Research Institute at the Royal Children's Hospital in Melbourne, Australia.
Until recently, doctors could only guess.
Now, Allen has found some good predictors by looking at skin prick test results.
The Skin Prick Test
In this test, commonly used by allergists, the skin is pricked and a tiny amount of the allergen is dropped onto the skin.
If the person is allergic to the substance, the body's allergic antibody, immunoglobulin E (IgE), is triggered and a chain reaction is set off, resulting in the patch of pricked skin becoming red and swollen.
This raised bump or small hive is called a wheal, and its size is known to give clues about allergies, Allen tells WebMD.
It's well-known by allergists, she says, that "kids who are 12 months old and have a skin prick with a wheal that is more than 4 millimeters means they are more than likely to have a reaction [if they eat the food they're suspected of being allergic to]."
The Remission Study
Allen and her colleagues followed 267 children with peanut allergies, some for years, to see if the size of the wheal over time could predict remission.
The children entered the study at an average age of 14 months -- the time when most infants first show peanut sensitivity, Allen says.
"We looked at the size of the skin prick wheal and followed them," Allen says. Once the size of the wheal that came after a prick fell sufficiently, the scientists would give a food challenge to see if the child had outgrown the allergy.
"We found that 20% of them outgrew it by 5 years of age,'' Allen says.
"We found the best predictor of remission was a falling skin prick test ... every year the reaction got a little smaller," she says.
The size of the wheal when children are younger can predict remission, too, Allen says.
"If the skin prick wheal is greater than 6 millimeters before 2 years of age, they are 1.5 times less likely to become tolerant," she tells WebMD.
The severity of the initial reaction, however, did not predict tolerance. "Kids with severe initial reactions are as likely to outgrow it," she says, as those whose first reaction was milder.
The results offer valuable information not just for parents whose children do outgrow it, she says, but also for those whose children are not likely to and therefore may need closer follow-up.
SOURCES: Scott David Nash, MD, Duke University Medical Center, Durham, N.C. Katie Allen, MD, PhD, pediatric gastroenterologist and allergist, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Australia. 2007 Annual Meeting of the American Academy of Allergy, Asthma and Immunology, San Diego, Feb. 23-27, 2007
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