"Participants who took a daily dose of egg product over the two-year study period were able to build up their bodies' resistance to the point where most of them could eat two scrambled eggs without a reaction," said A. Wesley Burks, from Duke University Medical Center.
The research could lead to offering food allergy sufferers protection from accidental ingestion of items that provoke reactions and, eventually, to induce complete or near-complete tolerance to those foods.
According to the European Federation of Allergy and Airways Diseases Patients' Associations, an estimated four per cent of adults and eight per cent of children in the 380m EU population suffer from food allergies.
As a result, the "free-from" food market has been enjoying sales growth, with of over 300 per cent reported in the UK since 2000, according to market analyst Mintel.
The most common food allergen ingredients and their derivatives are cereals containing gluten, fish, crustaceans, egg, peanut, soybeans, milk and dairy products including lactose, nuts, celery, mustard, sesame seed, and sulphites.
In the US, egg allergy is said to be one of the most common food allergies among children.
"Egg allergies cause a significant decrease in quality of life for many people, so this study is exciting in that it brings us a step closer to being able to offer a meaningful therapy for these people," said Burks.
The new claims from the Duke researchers and their collaborators at the University of Arkansas for Medical Sciences are based on results from a small study, funded by the National Institutes of Health and the two universities, of seven subjects (age range 1-7) who had a history of allergic reactions when they consumed eggs or egg products.
The participants were given small doses of powdered egg orally, mixed in food. "We started the subjects with a very small concentration of egg product - the equivalent of less than one-thousandth of an egg - and then we increased the dose every 30 minutes for eight hours in order to determine the highest dose that each subject could tolerate," explained Burks.
The children returned to the clinic every two weeks, and the researchers increased the doses until an equivalent of one-tenth of an egg was reached. This "maintenance dose" was continued for the rest of the study (24 months).
The researchers report that the children showed both an increase in tolerance to eggs and a decrease in the severity of their allergic reactions. Indeed, by the end of the study, the majority of the kids could tolerate two scrambled eggs with no adverse reactions.
"The protocol appears to be safe, to be well tolerated, and to offer protection against accidental ingestion reactions," wrote lead author in Ariana Buchanan in the Journal of Allergy and Clinical Immunology.
The success of the study, said the researchers, was based on food allergy "desensitisation". The technique, technically called oral immunotherapy (OIT), works on a cellular level to alter specific the response of white blood cells (lymphocytes) that play a part in the immune response during allergic reactions.
"Although the long-term induction of oral tolerance is the ultimate goal, even without such an effect, the use of OIT might provide a significant paradigm shift in the treatment of food allergy: active therapy instead of recommendations for strict avoidance and a prescription for epinephrine," concluded the researchers.
The study does have a notable limitation - the lack of a control group, but the researchers noted that their next studies will be of a double-blind, controlled design.
Two follow-up food allergy desensitization studies are underway, said Burks in a statement, the first of which is looking at the effects of higher doses of egg on further reductions on sensitivity or even allergy neutralisation.
The second study focuses on children who are allergic to peanuts, a condition that affects about one per cent of children under age 5, and its incidence has been on the rise over the past 15 years, according to Burks.
An extensive review, published earlier this week by the Global Allergy and Asthma European Network (GA2LEN) reported that the growing number of people suffering from allergies is due to changes in European diets over the past 30 years.
But by targeting several key areas, particularly how children are fed early in life, including breastfeeding, their early diet and increasing the use of pre- and probiotics could have a direct positive effect on the subsequent development of asthma and allergies.
Source: Journal of Allergy and Clinical Immunology, on-line ahead of print. doi: 10.1016/j.jaci.2006.09.016 Egg oral immunotherapy in nonanaphylactic children with egg allergy Authors: A. Buchanan, T. Green, S. Jones, A. Scurlock, L. Christie, K. Althage, P. Steele, L. Pons, R. Helm, L. Lee, A.W. Burks