Clinical spectrum of food allergy in children in Australia and South-East Asia: identification and targets for treatment

The prevalence of atopic diseases is increasing worldwide for reasons that are nor clean: Food allergies are the earliest manifestations of atopy. Thi s review defines the foods most commonly involved in allergic reactions and identifies an emerging group of syndromes in which food allergy is involve d. A study of the frequency of food allergies in Australia and South-Fast A sia has recently shown that egg, cow's milk rand peanut are the most common food allergens in Australia, but there were divergent results from differe nt regions of South-East Asia. It is not clear whether the differences in r eactivity to foods-are due to-genetic or cultural factors, but the findings raise the possibility that genetic susceptibility to food allergy may oper ate at the T-cell level modulated by the major histocompatibility complex. The Melbourne Milk Allergy Study defined a wide range of clinical symptoms and syndromes that could be reproduced by dietary challenge. a subsequent a nalysis of the infants with hypersensitivity to cow's milk and other multip le food proteins identified a new syndrome, multiple food protein intoleran ce of infancy. Food challenges demonstrated reactions developing slowly day s after commencement of low-allergen soy formula or extensively hydrolysed formula. Follow-up at the age of 3 years showed that most children with thi s disorder tolerated most foods apart from cow's milk, egg and peanut. atop ic dermatitis affects about 18% of infants in the first 2 years of life. In a community-based study we have shown a very strong association (RB: 3.5) between atopic dermatitis and infants with immunoglobulin E allergy to cow' s milk, egg or peanut. Family studies on these infants have shown a link be tween atopic dermatitis and the genomic region 5q31 adjacent to the interle ukin-4 gene cluster. Infantile colic (distress) affects 15-40% of infants i n the first 4 months of life. Many theories of causation have been proposed , bur a study horn our centre showed that dietary modification, particularl y that of breastfeeding mothers whose infants present with colic before the age of 6 weeks, alleviated symptoms. Colic associated with vomiting has be en attributed to gastro-oesophageal reflux (GOR). This has been considered primarily a motility disorder, but a secondary form resulting from food pro tein intolerance has been described recently. We have also recently identif ied a group of infants with distressed behaviour attributed to GOR who have failed to respond to H-2-receptor antagonists, prokinetic agents and multi ple formula changes. Symptoms resolved on commencement of an elemental amin o acid-based formula. In two-thirds of the patients, symptoms relapsed when challenged with low-allergen soy formula or extensively hydrolysed formula . We propose that a period of food protein intolerance is a part of the nor mal development of the immune system as it encounters common dietary protei ns in infancy and early childhood. Future targets for research are developm ent of appropriate dietary and management strategies for these entities and identification of genetic markers for these disorders.