Features
Food allergies are immunologic hyper-reactions to ingested substances considered non-pharmacologic, for the most part. Either the failure to develop or a breakdown in oral tolerance may be at fault in Immunoglobulin E (IgE) mediated allergy while inflammatory mediators are implicated in non-IgE cell mediated food allergies. Some food allergies have a mix of IgE and non-IgE mediation (Sampson, 2003). Generally, food allergies engage multiple classic immune mechanisms found in allergies (see ‘Allergies: general’).
Irrespective of aetiology, food allergies are the number one cause of generalized anaphylaxis treated in hospital accident and emergency (A&E) departments, and cover one-third of the total emergency room/A&E visits in the USA and the UK (respectively, Yocum & Kahn, 1994; Pumphrey & Stanworth, 1996). Anaphylaxis is when the smooth muscles vasodilate and constrict causing vasculature collapse because there is no blood pressure. Unknown, though, is why different individuals respond with different symptoms to different foods.
Food allergies can produce a range of discomfort and disease. Allergic immune dysfunction may create gastrointestinal, respiratory, or dermatologic symptoms like migraine, gluten enteropathy, Crohn's disease, eczema, wheeze, urticaria, irritable bowel syndrome or abdominal pain, and, in extreme cases, systemic anaphylactic shock (Del Rio Navarro & Sienra-Monge, 1993) (see ‘Inflammatory bowel disease’ and ‘Irritable bowel syndrome’). Besides producing discomfort and disease, these allergies can be fatal, and need serious consideration.
Food allergies are different from food intolerance and food aversions (Ferguson, 1992). Allergy requires an immune over-reaction, typically with elevated immunoglobulin E (IgE).