Review Article

The Diagnosis and Management of Food Allergy and Food Intolerances

J. L. Turnbull; H. N. Adams; D. A. Gorard

Disclosures

Aliment Pharmacol Ther. 2015;41(1):3-25. 

In This Article

Methods

A literature search was performed, using OVID MEDLINE, EMBASE and the Cochrane library, up until May 2014. Search terms included 'food allergy' 'food intolerance', 'IgE-mediated', 'non-IgE mediated', 'cow's milk protein allergy', 'Protein-induced enterocolitis syndrome', 'anaphylaxis', 'immunotherapy', 'eosinophilic oesophagitis', 'eosinophilic gastroenteritis', 'lactose intolerance', 'fructose intolerance', 'gluten sensitivity'. The articles returned by the search were selected based on English language and relevance to this review. Important articles identified in the most recent published reviews were also then appraised.

What is Food Allergy?

Food allergy is an adverse immune-mediated response, which occurs reproducibly on exposure to a given food and is absent during avoidance. A diagnosis of food allergy requires evidence of sensitisation and specific symptoms on exposure to a particular food. The immune response in food allergy can be classified into IgE-mediated, non-IgE-mediated or a mixture of both (Figure 1). IgE-mediated food allergy requires food allergen sensitisation (with the development of serum specific IgE antibody to a food allergen), and secondly the development of signs and symptoms on exposure to that food. In non-IgE-mediated food allergy, T-cell-mediated processes predominate and there may be histological evidence of an underlying immune process such as eosinophilic inflammation of the gastrointestinal tract.

What is Food Intolerance?

Other types of undesirable reactions to food are termed food intolerances. These non-allergic food reactions do not involve the immune system. Some food intolerances involve an organic pathophysiological process, e.g. lactose intolerance occurs as a consequence of deficiency in the enzyme that breaks down lactose. However, some food intolerances cannot be readily explained by currently understood organic processes, e.g. many of the food intolerances reported in irritable bowel syndrome (IBS) patients.

Prevalence of Food Allergy and Other Adverse Reactions to Food

Perceptions of adverse reactions to food, whether allergy or intolerance are common. In a United Kingdom household survey, 20% of the population reported food intolerances. However when double-blind placebo-controlled food challenges were performed, the prevalence of true reactions to food was less than 2%.[5] In a German study, one-third of respondents to a postal questionnaire reported reactions to food, but subsequent double-blind placebo-controlled food challenges identified a true prevalence of adverse food reactions of 3.6%, of which more than two thirds were IgE-mediated.[6] Women were more likely to have both self-reported symptoms and blind challenge-confirmed adverse food reactions.[7]

The prevalence of true immunologically mediated food allergy is difficult to measure. There are large variations in study methodology, from those relying on self-reporting questionnaires that tend to vastly exceed the true prevalence due to their reliance on lay perceptions of allergy, to studies using more rigorous double-blind placebo-controlled food challenges but only including small numbers of patients. What is clear is that food allergy is more common in children than adults, and seems to be increasing in prevalence in many countries.[8–11] The prevalence of food allergy across the whole US population is approximately 2.5–3% when objective measures, such as serological testing and food challenges, are used.[11,12] While prone to overestimation, population surveys of US children yield self-reported prevalences of food allergy that vary from 4% in the 2007 National Health Interview Survey,[13] to 8% in another population survey of US children.[14] More objective serological data from the 2005 National Health and Nutrition Examination Survey, established that 4.2% of US children aged 1–5 years had positive food-specific serum IgE serology results for peanut, milk, egg white or seafood. The prevalence of elevated specific IgE reduced with age to 3.8% in 6–19 year olds, and 1.3% in those over 60 years.[12]

Since relatively few epidemiological studies have used the gold standard of diagnosis – the double-blind placebo-controlled food challenge, the true prevalence of food allergy remains elusive, and a US-based meta-analysis from 2010 was forced to give a range from 1–10%.[9,15] The ongoing European Union-commissioned birth cohort study Euro Prevall will provide important epidemiological data on allergy in Europe.[16]

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