Mechanisms in adverse reactions to foods: a review

Human diet consists of an enormous variety of both plants and animal proteins, many of which are potentially immunogenic. Industrial processing of foods and digestion in the gastrointestinal tract causes changes and breakdown of proteins into peptides, which are also potential immunogens. Foods commonly known to cause allergic reactions are fish, milk, eggs, fruits, vegetables, nuts, legumes and meat. Once sensitised to a particular antigen, subsequent exposure may result in a marked and immediate reaction characterised by vomiting, diarrhoea, abdominal cramps, itching and swelling of the mouth and skin, dizziness and occasionally systemic anaphylaxis. Allergic reactions involve complex processes and interactions between the allergen and immunological components in the digestive tract such as antigen absorption, processing and presentation, T cell and B cell activation, development of oral tolerance or allergic sensitivity, antigen-specific IgE antibody synthesis. Allergen binding to allergen-specific mast cell membrane-bound IgE antibodies triggers mast cell degranulation. This results in the release of histamine and other chemotactic mediators responsible for clinical symptoms.