Early exposure to food allergens may increase tolerance

The study, looking at the risk of developing food allergy in premature or low-birth-weight children, found no difference between the normal and premature babies, challenging the hypothesis that immature gastrointestinal tracts may boost food allergy development. "To the best of our knowledge, this population-based study is the first to examine prematurity or low birth weight and the risk of developing food allergy,"​ wrote lead author Joel Liem from the University of Manitoba. "Our data suggest that no association exists between gestational age and birth weight with the development of IgE-mediated food allergies. As a result, the theory that an immature gut mucosa results in increased permeability to large-molecular-weight proteins and predisposes the baby to early sensitization needs to be questioned,"​ he added. 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. Previous studies had indicated that immature gastrointestinal tracts as found in premature babies result in an increased uptake of food antigens, but limited studies have investigated the immunologic response of preterm or low-birth-weight infants to dietary antigens, said the researchers in the current issue of Journal of Allergy and Clinical Immunology.​ The researchers analysed 13,980 children were born in 1995 and living in the province of Manitoba, and of these, 592 children were found to have food allergy. When the data was analysed with respect to birth weight and maturity, no association with food allergy was observed. "Prematurity and low birth weight are not associated with a change in risk for development of food allergy in childhood,"​ said the researchers. The researchers did find that food allergy was associated with a maternal history of asthma and food allergy, however. "The theory is that at a young age (ie. less than 3 years), an immature and permeable gastrointestinal tract will result in increased antigen uptake. Thus, highly allergenic foods may be absorbed more easily, increasing the risk for sensitization,"​ said Liem. "However, our large, population-based epidemiologic study does not support [this]. A possible mechanism preventing sensitization might be the development of immunologic tolerance to orally ingested allergens in premature infants. ​​"Such tolerance might result from interaction of high antigen concentration with the immature immune system of the preterm infant,"​ he said. "These data prompt us to ask whether it may be possible that introducing highly allergenic proteins (such as peanut) early in life would tolerise (as opposed to sensitise) a child to that particular antigen?"​ said the researchers. They called for carefully designed and monitored studies to identify the best approach to the introduction of foods for infants and young children. An extensive review, published towards the end of 2006 by the Global Allergy and Asthma European Network (GA²​LEN) 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​ May 2007, Volume 119, Issue 5, Pages 1203-1209 "The risk of developing food allergy in premature or low-birth-weight children" ​Authors: J.J. Liem, A.L. Kozyrskyj, S.I. Huq and A.B. Becker