Evaluation of food allergies and sensitivities

Food allergy is defined as an adverse immunologic response to a food protein.[1]Sicherer SH, Sampson HA. 9. Food allergy. J Allergy Clin Immunol. 2006 Feb;117(2 Suppl Mini-Primer):S470-5. http://www.ncbi.nlm.nih.gov/pubmed/16455349?tool=bestpractice.com Although approximately 19% of adults in the US have a perceived adverse reaction to food, only 10.8% have a convincing history of true food allergy, according to a cross-sectional survey study.[2]Gupta RS, Warren CM, Smith BM, et al. Prevalence and severity of food allergies among US adults. JAMA Netw Open. 2019 Jan 4;2(1):e185630. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2720064 http://www.ncbi.nlm.nih.gov/pubmed/30646188?tool=bestpractice.com In a separate study of US households, approximately 11% of children were perceived by their parents to have a food allergy, but only 7.6% had a convincing history of true food allergy.[3]Gupta RS, Warren CM, Smith BM, et al. The public health impact of parent-reported childhood food allergies in the United States. Pediatrics. 2018 Nov 19;142(6):e20181235. https://pediatrics.aappublications.org/content/142/6/e20181235.long http://www.ncbi.nlm.nih.gov/pubmed/30455345?tool=bestpractice.com

People who believe they have a food allergy may suffer from a metabolic intolerance to a particular food; for example, lactose intolerance. Others may be sensitive to a particular pharmacologically active component of food such as caffeine or tyramine. Some people may mistake bacterial food poisoning as a reaction to a particular food.[1]Sicherer SH, Sampson HA. 9. Food allergy. J Allergy Clin Immunol. 2006 Feb;117(2 Suppl Mini-Primer):S470-5. http://www.ncbi.nlm.nih.gov/pubmed/16455349?tool=bestpractice.com [4]Ebisawa M, Ito K, Fujisawa T; Committee for Japanese Pediatric Guideline for Food Allergy, The Japanese Society of Pediatric Allergy and Clinical Immunology, The Japanese Society of Allergology. Japanese guidelines for food allergy 2017. Allergol Int. 2017 Apr;66(2):248-64. http://www.allergologyinternational.com/article/S1323-8930(17)30005-9/fulltext http://www.ncbi.nlm.nih.gov/pubmed/28285847?tool=bestpractice.com Although all of these scenarios involve food, they do not result from an abnormal immune response to a particular food protein and therefore cannot be considered a true food allergy.[5]Zopf Y, Baenkler HW, Silbermann A, et al. The differential diagnosis of food intolerance. Dtsch Arztebl Int. 2009 May;106(21):359-69. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2695393 http://www.ncbi.nlm.nih.gov/pubmed/19547751?tool=bestpractice.com Rather, some of them, such as lactose intolerance and sucrase-isomaltase deficiency, are considered nonimmune food intolerances, and others, such as tyramine and sulfite reactions, are considered nonimmune food sensitivities.

It is important that people with suspected food allergy are investigated and followed up appropriately so that they do not unnecessarily avoid food and impair their quality of life.[2]Gupta RS, Warren CM, Smith BM, et al. Prevalence and severity of food allergies among US adults. JAMA Netw Open. 2019 Jan 4;2(1):e185630. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2720064 http://www.ncbi.nlm.nih.gov/pubmed/30646188?tool=bestpractice.com

Pathophysiology

Food allergies can be classified into disorders that are IgE-mediated, cell-mediated, or a combination of the two.[6]Sicherer SH. Food allergy. Lancet. 2002 Aug 31;360(9334):701-10. http://www.ncbi.nlm.nih.gov/pubmed/12241890?tool=bestpractice.com

IgE-mediated food allergies result from abnormal sensitization to a food allergen that results in specific IgE production. However, a positive skin prick test or IgE test on its own does not indicate that a patient has a food allergy; it only means that they are sensitized to a food. Only the history or an oral food challenge can identify true food allergens. Once produced, food-specific IgE binds onto mast cells. When the particular food is subsequently ingested, the food is broken down and absorbed. The food antigen then binds to the IgE on the mast cells leading to mast-cell degranulation and release of mediators that cause the signs and symptoms of the allergic reaction.[6]Sicherer SH. Food allergy. Lancet. 2002 Aug 31;360(9334):701-10. http://www.ncbi.nlm.nih.gov/pubmed/12241890?tool=bestpractice.com IgE-mediated food disorders include anaphylaxis and oral allergy syndrome.

Cell-mediated reactions involve T cells and may occur several hours to days after ingesting the offending food.[6]Sicherer SH. Food allergy. Lancet. 2002 Aug 31;360(9334):701-10. http://www.ncbi.nlm.nih.gov/pubmed/12241890?tool=bestpractice.com Food protein-induced enterocolitis, enteropathy, proctocolitis, and celiac disease are examples of cell-mediated food-allergic diseases.

Mixed IgE- and cell-mediated food diseases include atopic dermatitis and the eosinophilic gastroenteropathies such as eosinophilic esophagitis.[6]Sicherer SH. Food allergy. Lancet. 2002 Aug 31;360(9334):701-10. http://www.ncbi.nlm.nih.gov/pubmed/12241890?tool=bestpractice.com

Nonimmune food intolerances often result from deficiencies in the enzyme that breaks down the food component into absorbable substrates in the small intestine.[7]Heyman MB; Committee on Nutrition. Lactose intolerance in infants, children, and adolescents. Pediatrics. 2006 Sep;118(3):1279-86. https://pediatrics.aappublications.org/content/118/3/1279.full http://www.ncbi.nlm.nih.gov/pubmed/16951027?tool=bestpractice.com

Nonimmune food sensitivities to biogenic amines (such as tyramine) or to food additives (such as monosodium glutamate) are more controversial and are debated vigorously in the literature.[8]Jansen SC, van Dusseldorp M, Bottema KC, et al. Intolerance to dietary biogenic amines: a review. Ann Allergy Asthma Immunol. 2003 Sep;91(3):233-40. http://www.ncbi.nlm.nih.gov/pubmed/14533654?tool=bestpractice.com [9]Geha RS, Beiser A, Ren C, et al. Multicenter, double-blind, placebo-controlled, multiple-challenge evaluation of reported reactions to monosodium glutamate. J Allergy Clin Immunol. 2000 Nov;106(5):973-80. http://www.ncbi.nlm.nih.gov/pubmed/11080723?tool=bestpractice.com However, sensitivities to sulfites found in foods such as red wine and dried fruit have been confirmed as a trigger of bronchospasm in sulfite-sensitive asthmatic patients.[10]Simon RA. Update on sulfite sensitivity. Allergy. 1998;53(46 Suppl):78-9. http://www.ncbi.nlm.nih.gov/pubmed/9826006?tool=bestpractice.com