Adverse Reactions to Foods
Many consumers consider a wide variety of adverse reactions associated with the ingestion of foods to be “food allergies.” While adverse reactions may occur for a variety of immunological, toxicological, or metabolic reasons only a small fraction of these are related to food allergies (figure II-1). The signs and symptoms associated with these reactions can range from oral irritation and swelling to cardiovascular collapse (Jackson, 2003). Although adverse reactions caused by microbial and toxicological agents can affect any most individual, immunonlogical reactions only affect a small group of sensitive individuals. Reactions caused by the presence of toxic compounds such as histamine in seafood (e.g., scombroid poisoning) or from metabolic (e.g., lactose intolerance) are not true food allergies. The nomenclature used to describe these well documented reactions in sensitive individuals is not consistent in the scientific literature. Generally, reactions not involving immune responses are termed food intolerances (Johansson et al., 2001; Sampson, 2004).
Immunological responses to foods, including food allergies, occur in a sensitive population of individuals. The major immunological responses to foods, termed food hypersensitivities, can be divided into two major categories based on mechanism: (1) immunoglobulin E (IgE)-mediated hypersensitivity (e.g., oral allergy syndrome, anaphylaxis) and (2) non-IgE-mediated hypersensitivity (e.g., celiac disease, food protein-induced enterocolitis) (Johansson et al., 2001; Wershil et al., 2002, Sampson, 2004). A group of food-related disorders (e.g., allergic eosinophilic gastropathies, atopic dermatitis) may involve both IgE- and non-IgE-mediated immune mechanisms (Sampson, 2004). For the purposes of this report, the term “food allergy” will be used to describe IgE-mediated immune responses resulting from the ingestion of specific foods (Johansson et al., 2001; Jackson, 2003; Sampson, 2004). The most severe and immediately life-threatening adverse reactions to foods are associated with IgE- mediated hypersensitivity (Johansson et al., 2001; Jackson, 2003; Zarkadas et al., 1999).