New Therapy for Food Allergy Builds Tolerance Through Exposure

New therapy for food allergies exposes patients to small doses of the allergen.

March 27, 2010, 10:42 AM

March 28, 2010— -- Researchers are applying an old principle to a new treatment for food allergy -- fight fire with fire.

The technique is called oral immunotherapy, and it essentially attempts to build a child's tolerance by gradually exposing them via oral ingestion to the food proteins that typically trigger a severe allergic reaction, or anaphylactic shock.

"The purpose of immunotherapy is to change your immune response over a period of months to years," said Dr. Wesley Burks, chief of pediatric allergy and immunology at Duke University and a pioneer in oral immunotherapy. "So you start off being allergic and at the end of that therapy, you are no longer allergic."

Right now, the treatment is only available in clinical trials because it is experimental. While some allergists may offer it in their practices, those investigating the treatment caution against routinely attempting this approach because doing so can have unpredictable, and sometimes dangerous, results.

Still, many allergists and patients are banking on the promise of oral immunotherapy because there are so few treatment options for food allergy aside from avoidance and keeping injectible epinephrine handy at all times.

Oral immunotherapy involves first giving the child a very small dose -- as little as a thousandth of a percent -- of the protein he or she is allergic to, whether it's egg, peanut or milk.

The physician will then gradually increase the dose, usually over a period of weeks. In the meantime, the child takes a "maintenance" dose of the allergen at home every day.

Early results of one of the first randomized controlled trials -- the gold standard of evidence-based medicine -- of oral immunotherapy for peanut allergies were presented last month at the American Academy of Allergy, Asthma, and Immunology meeting in New Orleans.

Burks and his team found that after 48 weeks of oral immunotherapy food-allergic children could tolerate eating the equivalent of 20 peanuts.

Children who were on a sham treatment, or a placebo, could only eat the equivalent of 1.5 peanuts.

"Certainly the early studies indicate that it is promising," Burks said. However, he warned that the research "isn't quite there yet."

Exposure Treatment Can Be Unpredictable

Dr. Hugh A. Sampson, of the Jaffe Food Allergy Institute at Mount Sinai Medical Center in New York who is involved in a randomized controlled trial of oral immunotherapy for egg allergy, said the treatment can bring unpredictable risks.

"Even under very conservative protocols," he said, "we still see adverse reactions."

Most reactions are mild -- abdominal pain, vomiting, swelling -- but trials have reported cases of anaphlaxis, some in the physician's office while upping the dose, others at home while taking maintenance dosing.

"We especially don't want parents trying this at home because kids can have these fairly severe reactions," Sampson said.

The next step, he said, is to investigate which will be least likely to have these adverse reactions, as well as which patients will benefit most from the treatment.

Another issue to consider is whether children will maintain their tolerance once they've been off oral immunotherapy for a longer period of time.

Given the amount of research that still needs to be done, Burks says it will likely take several years before the treatment is widely available.

The concept of oral immunotherapy is not entirely new, however. Sampson said it dates back to the early 20th century, and was researched more extensively in the 1940s and '50s as a treatment for food allergy.

It fell off sometime after that, but was researched as a treatment for penicillin allergy.

By the late '90s, research into oral immunotherapy for food allergy was revived, Sampson said, but was limited to open-label trials, in which all patients received the therapy. These types of trials do not carry as much weight as randomized controlled trials.

Food Allergies in Children Rising

Another therapy -- sublingual immunotherapy, or SLIT -- uses a similar approach, but instead of fully ingesting the proteins, they are placed under the patient's tongue.

Sampson said that the therapy typically carries a lower risk for adverse reactions, but it is not necessarily as effective as oral immunotherapy.

"It doesn't seem to desensitize the patient as quickly," he said, "but it may [do so] over a longer period."

Burks said the prevalence of children with food allergies is rising and is higher now than ever before, although the reasons are still unclear. One explanation may be what researchers call the "Hygiene Hypothesis," which holds that kids aren't being exposed to the appropriate bacteria in order to adequately engage their immune systems.

Or, Sampson says, it may have something to do with a Western diet and lifestyle. Asian patients, for example, have a lower prevalence of peanut allergy. He said that could have something to do with the way the food is prepared: Americans tend to eat peanuts raw, while Asians cook them. Heating a protein causes changes to its structure, and that could potentially make it more allergenic, he said.

Either way, he said oral immunotherapy is promising, particularly for those food allergies that children don't outgrow. (Many outgrow egg and milk allergies after the first five or six years of life, but 80 percent of patients with peanut allergy will retain it into adulthood.)

"These are the first studies for food allergy in a long time," Burks said, "and they have given us some hope that we can have an ... effective, proactive therapy in the next several years."

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