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Prevalence and incidence of food allergies and food intolerance

Project Code: T07023;
Publication:

Venter, C., Pereira, B., Voigt, K., Grundy, J., Clayton, C. B., Higgins, B., Arshad, S. H. and Dean, T. (2009). Factors associated with maternal dietary intake, feeding and weaning practices, and the development of food hypersensitivity in the infant. Pediatric Allergy and Immunology. 20: 320-327.
Venter, C., Arshad, S. H., Grundy, J., Pereira, B., Clayton, C. B., Voigt, K., Higgins, B. and Dean, T. (2010). Time trends in the prevalence of peanut allergy: three cohorts of children from the same geographical location in the UK. Allergy. 65: 103-108.

31/08/2006

Institute of Medicine, Health and Social Care, University of Portsmouth
Dean, T

Food hypersensitivity (FHS) is believed to affect 1.5% of adults and 6–8% of children (1-4). Very few studies regarding population prevalence of FHS have been published, and not all of them used the gold standard method for diagnosis of food allergy: the Double Blind Placebo Controlled Food Challenge (DBPCFC), particularly for the diagnosis of non-IgE mediated allergy. Even fewer studies have addressed the prevalence of FHS in children. The most quoted study was performed in the USA more than 20 years ago and determined that 7.6% (cumulative incidence) of the children (0-3 years) were truly food allergic (1). In a recent German study (3), 4.2% of children (0 – 17 years) were found to suffer from FHS.

It was therefore the aim of this study to 1) investigate the prevalence and incidence of FHS in children, looking primarily at the cumulative incidence of FHS over the first three years of life and the prevalence of FHS in older children and teenagers (6, 11 and 15 years) and 2) establish temporal changes in sensitisation to foods and FHS over the last two decades.

To recruit the birth cohort, all pregnant women with an estimated delivery time 1 September 2001– 31 August 2002 were approached at antenatal clinics to participate in this study. For the school cohorts, the target population was approached via the schools after discussions with the Isle of Wight Education Authority and all head teachers for primary, middle and high schools. Children in the birth and school cohorts were approached for skin prick tests (SPT) to a standard battery of food allergens (milk, egg, wheat, peanut, sesame, and cod fish), aero-allergens (house dust mite Dermatophagoides pteronyssinus, cat and grass) and other allergens as identified by history. Children were identified for food challenges taking into account their reported history and SPT result. Challenge protocols were designed by the research dietitian based on procedure manuals, guidance papers, current research literature and consultation with experts in food allergy.

For the birth cohort, a total of 969 pregnant women were recruited for the study (91% of the target population). Over the course of the three years 942 (97.2%) children were seen at either one, two or three years, with 807 (83.3%) children seen at one, two and three years. At one, two and three years, the rate of sensitisation to any food allergen was 1.9%, 3.8% and 4.5%. Over the course of the three years 5.3% children had a positive SPT to any food in the predefined panel.

Adverse reactions to food were reported by 7.2 % parents at 12 months of age, 8.4% at two years and 8.3% at three years. Of the 807 children seen at one, two and three years, 272 (33.7%) reported a food related problem. Based on OFC and a good clinical history, the prevalence of FHS was 3.8% at one year, 2.5% at two years and 3.0% at three years. Based on DBPCFC and a good clinical history, the prevalence of FHS was 3.0% at one year, 2.1% at two years and 2.9% at three years. Cumulative, by 3 years of age, 6.0% of children were diagnosed with FHS based on OFC and history and 5.0% children based on DBPCFC and history. Overall the foods implicated in this study were milk, egg, peanut, corn, potato, tomato, salicylates and wheat.

Only 16.1% of children who were seen at one, two and three years and reported a food related problem were diagnosed with FHS by means of an OFC and history and 12.9% by means of a DBPCFC and history.

Comparing the information of the three year olds with children (aged four years) born 12 years earlier on the Isle of Wight, the results indicated that there was no increase in sensitisation to food allergens (p=0.3) or in the prevalence of peanut allergy (p=0.1) (based on OFC results from both studies). Very importantly, in our study we were able to compare our FHS incidence rates with that of Bock (2). In this USA study, of the 501 children enrolled into the study, 37 (7.4%) were diagnosed with FHS by means of either OFC or DBPCFC. In our study, of the 969 children enrolled into the study, 6.0% (58/969, CI: 4.6 – 7.7) children were diagnosed with FHS based on OFC and history and 5.0% (48/969, CI: 3.7 – 6.5) children based on DBPCFC and history. Using either the OFC or DBPCFC outcome, the difference in incidence was not statistically significant (p=0.30 for OFC and p=0.06 for DBPCFC).

For the school cohorts, 3.6% (6 year olds), 5.1% (11 year olds) and 4.9 % (15 year olds) had a positive SPT to any of the food allergens. A total of 94 (11.8%) six-yearolds reported a problem with a food or food ingredient, 11.6% eleven- and 12.4% fifteen-year-olds. Based on open food challenge and/or suggestive history and positive skin tests, the prevalence of food hypersensitivity was 2.6% in the six year old cohort. Based on double blind challenges, a clinical diagnosis or suggestive history and positive skin tests, the prevalence was 1.6%. The corresponding figures were 2.3% and 1.4% for the eleven year olds and 2.3% and 2.1% for the fifteen year olds. Amongst the school cohorts the foods most commonly implicated in FHS were milk and milk products, peanut, wheat, banana, sesame, tree nuts, egg, shellfish, gluten (coeliac disease), green beans, kiwi, tomato and additives. FHS was confirmed by OFC and a good clinical history in only 21% (20/94) six year olds, 20% (18/90) eleven year olds and 18% (17/94) of the fifteen-year-olds who reported a food problem.

The key findings from this study therefore indicate that, reported adverse reactions to foods are common in all age groups, but rates of diagnosed FHS are low. Looking at the rates of FHS in each age group, the FHS rate ranged between 1.4% based on DBPCFC and a good clinical history at age 11 years and 3.0% based on DBPCFC and a good clinical history at one year. Additionally, considering the birth cohort, we have found that sensitisation to foods and diagnosed FHS have not increased over the last two decades. In the light of the discrepancy between reported and diagnosed FHS, the major implication of this study is the need for accurate diagnosis to prevent children being on unnecessary restricted diets. This may be associated with inadequate nutrition at this important period of growth and development. This has an important implication as there are a limited number of Allergy Specialists and Allergy Centres available in the UK. Community dietitians and GPs are often left with having to make a clinical diagnosis of FHS without the possibility of performing SPT or food challenges.

They very often also do not know how to interpret specific IgE levels. This study therefore highlights the need for more allergy trained health professionals in order to rule out FHS in about 20% of the UK population who claims to suffer from FHS as well as managing FHS in about 1.5 – 3.8% of the UK population who are truly clinically allergic.

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