06 July 2009

'Learning' to overcome food allergy

Experiments show it's possible to develop resistance to peanuts, eggs and more.


Doctors have long used allergy shots to desensitise children and adults to environmental allergens such as bee stings, pollen, mould and dust mites.

Now researchers are trying to apply that theory to food allergies, through processes called oral immunotherapy and sublingual immunotherapy.

They believe they can build up a child's tolerance for a food that prompts an allergic reaction by exposing the child to tiny amounts of that food.

"It is something that has been recently put into play," said Dr Michael Pistiner, an allergist in Leominster, Mass., and a spokesman for the American Academy of Allergy, Asthma & Immunology. "More and more of these trials have been started. It does seem to be very promising. It's very exciting."

Studies are promising
Trials involving eggs, peanuts and milk have produced positive results, said Dr Scott H. Sicherer, an associate professor of paediatrics at the Jaffe Food Allergy Institute at the Mount Sinai School of Medicine and chairman of the allergy and immunology section for the American Academy of Paediatrics.

"The studies are promising in that some individuals are able to get to high doses of the food used in treatment," Sicherer said.

Sublingual immunotherapy works by placing an extract of the food allergen under the child's tongue. The membranes of the mouth absorb trace amounts of the allergen, absorbing just enough to desensitise the immune system without prompting an allergic reaction.

Oral immunotherapy takes it a step further by having children eat tiny amounts of the allergen. "The approach involves ingesting an extremely small and then gradually increasing amount of the food under medical supervision, with the hope of getting to an amount that is not causing reactions and is more substantial in dose," Sicherer said.

However, both Sicherer and Pistiner warn that these therapies are still in the experimental stage, and many questions remain.

"All of the experts working in this treatment currently believe it is too early to attempt widespread use and that much more needs to be done to see if this is a viable treatment," Sicherer said.

’Do not try this at home’
For one thing, there's still a risk of severe allergic reaction prompted by even the tiny amounts used in immunotherapy.

"People have significant reactions trying to do this, including anaphylaxis and not all can move ahead with dosing," Sicherer said.

Researchers also are not sure how deeply ingrained the tolerance becomes in a child undergoing oral or sublingual immunotherapy.

"Is there ever a time you can stop taking it, or does it only work as long as you're taking your maintenance dose?" Pistiner asked. "Does it give you complete ability to eat that food, or does it only help prevent reactions when trace amounts of the foods are consumed?"

For example, if you're allergic to pine nuts, will immunotherapy allow you to eat pine nuts as you like, or will it only prevent you from having an allergic reaction when you eat a food processed on equipment that also processes pine nuts?

The doctors agree on one other point: This is absolutely not something a person should try at home.

The amounts of food given allergic children are measured out precisely, and delivered under the watchful eyes of doctors ready to step in and treat any side effects or allergic reactions at a moment's notice.

"This is an experimental therapy that should only be undertaken under the direction of a trained allergist," Pistiner said. "Doing this at home is absolutely not safe." – (HealthDay News, July 2009)

Read more:
Exposure to peanuts ups tolerance


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Dr Morris is the Principal Allergist at the Cape Town and Johannesburg Allergy Clinics with postgraduate diplomas in Allergology, Dermatology, Paediatrics and Family Medicine dealing with both adult and childhood allergies. obesity and diabetes societies and runs a trial centre for new drugs.

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