Outgrowing allergies to milk and egg may no longer be the case, as new research from the US suggests the allergies are more persistent than first thought.
Over the course of 13 years, researchers from the Johns Hopkins Children's Center followed 800 patients with milk allergy and nearly 900 with egg allergy, and found that the allergies persisted well into the school years and beyond.
The studies are published in the November and December issues of the Journal of Allergy and Clinical Immunology.
"The bad news is that the prognosis for a child with a milk or egg allergy appears to be worse than it was 20 years ago," said lead researcher Robert Wood. "Not only do more kids have allergies, but fewer of them outgrow their allergies, and those who do, do so later than before."
Some may say that every cloud has a silver lining, with the possible opportunities this presented to the booming free-from food market, which has been enjoying sales growth of over 300 per cent in the UK alone since 2000, according to market analyst Mintel.
An estimated four per cent of adults and eight per cent of children in the 380m EU population suffer from food allergies, according to the European Federation of Allergy and Airways Diseases Patients' Associations.
Previously, studies have reported that 75 per cent of children with milk allergy outgrew their condition by age 3, but the new study indicated that only 20 per cent of children may outgrow their allergy by four years of age. By eight years of age, 42 per cent of the children had outgrown the condition, while 79 per cent were allergy-free by age 16.
Similar trends were seen in the egg-allergy group, report the researchers, with only four per cent of the children studied outgrowing this allergy by four years of age. Only 37 per cent were allergy-free by time they reached ten years of age, which rose to 68 per cent by age 16.
Wood and co-workers reported a correlation between a child's blood levels of milk and egg antibodies (IgE) - the immune chemicals produced in response to allergens - and disease behaviour: The higher the level of antibodies, the longer the time to outgrow the allergy.
"Our data suggest that this does not happen as early as previously thought. Furthermore, we have identified an egg IgE level of at least 50 kU/L as a marker of persistent egg allergy," wrote the authors.
In terms of milk, they added: "Our findings stand in marked contrast to the study that is most often quoted, which found that 75 per cent of children with IgE-mediated milk allergy were tolerant by the age of three years. One positive finding is that patients did continue to achieve tolerance well into adolescence."
In September 2006, Dr. Ronald van Ree from the University of Amsterdam told attendees at the BA Festival of Science in England that recent advances in biotechnology have identified the specific molecules in foods that induce food allergies. Such knowledge could also lead to genetic engineering techniques to change these molecules so that they no longer cause an allergic response, he said.
Allergen labelling regulations that came into force in the EU in November 2005 require companies to label all pre-packed foods if they contain any of the 12 listed allergenic foods as an ingredient.
The mandatory inclusion on food labels of the most common food allergen ingredients and their derivatives covers cereals containing gluten, fish, crustaceans, egg, peanut, soybeans, milk and dairy products including lactose, nuts, celery, mustard, sesame seed, and sulphites.
Sources: Journal of Allergy and Clinical Immunology
November 2007, Volume 120, Issue 5, Pages 1172-1177
"The natural history of IgE-mediated cow's milk allergy"
Authors: J.M. Skripak, E.C. Matsui, K. Mudd and R.A. Wood
Journal of Allergy and Clinical Immunology
December 2007, Volume 120, Issue 6, Pages 1413-1417
"The natural history of egg allergy"
Authors: J.H. Savage, E.C. Matsui, J.M. Skripak and R.A. Wood