World Digestive Health Day WDHD – May 29, 2016 FOOD ALLERGY AND THE DIGESTIVE TRACT SHEILA E. CROWE, MD, FRCPC, FACP, FACG, AGAF Professor of Medicine Division of Gastroenterology, Department of Medicine University of California San Diego, California, USA DEFINITION AND FORMS OF FOOD ALLERGY Adverse immune responses to proteins in a food constitute a food allergy. All other forms of adverse reactions to foods (ARF) are non-immune reactions (see Figure 1), commonly referred to as food intolerances, which comprise physiological, pharmacological, psychological, and unknown mechanisms. 1 A clinician’s ability to discern food allergies from food intolerances is absolutely essential, as prognosis and management of allergy and intolerance require vastly different approaches.2, 3 Figure 1. GOVIND K. MAKHARIA, MD, DM, DNB, MNAMS Professor Department of Gastroenterology and Human Nutrition All India Institute of Medical Sciences Ansari Nagar, New Delhi, India Classical food allergy or hypersensitivity results from a humoral response involving immunoglobulin E (IgE) antibody directed to specific proteins. These antibodies bind to effector cells, basophils in the circulation, mast cells in skin, and mucosal tissues of the gastrointestinal (GI) and respiratory tracts and upon exposure to the offending food, these cells degranulate, releasing histamine and other mediators which give rise to a variety of symptoms.4 Other forms of food allergy arise from an abnormal cellular response to specific foods. Celiac disease is an example of a T cell-mediated disease.5 Specific peptide sequences of proteins known as gluten can activate T lymphocytes in genetically susceptible individuals. The T cells release cytokines and other cellular events lead to the enteropathy which characterizes the disease. Celiac disease (discussed elsewhere) is unique as it is both a food allergy and an autoimmune condition. Food allergy can be mediated by eosinophils that infiltrate the entire luminal digestive tract.6 Only the mucosal layer of the esophagus is involved in eosinophilic esophagitis (EoE), but in the remaining rare forms of the disease that involve the stomach, intestine, and/or colon, eosinophils are found in the mucosa (most common), the muscular layer, and/or the serosa. CLINICAL PRESENTATIONS IgE-mediated responses to food allergy present a wide range of clinical manifestations with a rapid onset, a spectrum that ranges from self-limited, localized hives to potentially fatal anaphylaxis. Hives and angioedema are the most common symptoms of food allergy. GI, cardiovascular, and/or respiratory systems may be affected. The most serious symptom of IgE-mediated food allergy is generalized anaphylaxis. The primary manifestations of a GI allergic reaction are a) GI anaphylaxis (nausea, vomiting, abdominal pain, diarrhea) which typically develops along with allergic symptoms beyond the digestive tract, such as wheezing and urticarial and b) the oral allergy syndrome.7 GI allergy symptoms typically present within a span of a few minutes to a couple of hours after ingesting the culprit food. A rare type of anaphylaxis—food-dependent exercise-induced anaphylaxis—triggers an anaphylactic response when an individual consumes an offending food within 2 to 4 hours of participating in exercise, though no allergic consequences occur if the individual ingests that same food and does not exercise.2 World Digestive Health Day WDHD May 29, 2016 WGO Handbook on DIET AND THE GUT 25
WGO Handbook on Diet and the Gut_2016_Final
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