Allergy and types of hypersensitivity

Food Toxicology 2(2+0)
Lesson 20 : Food Intolerance and Allergy

Allergy and types of hypersensitivity

Many people eat a variety of foods and show no ill effects; however, a few people exhibit adverse reactions to certain foods. Food sensitivities refer to the broad concept of individual adverse reactions to foods. Food sensitivities are reproducible, unpleasant reactions to specific food or food ingredients. There are many types of adverse reactions to foods, e.g., hives, headaches, asthma, and gastrointestinal complaints.

Foods contain many proteins, but only a few of them are allergens. Virtually all allergens are proteins, but not all proteins are food allergens. Allergens tend to be the most abundant protein found in a particular food. Most allergenic foods contain multiple allergens; for example, egg white contains 20 proteins, of which 5 or 6 are allergenic. Most allergens gens are stable to digestion and processing, Heat and processing tend to change the tertiary structure of food proteins, but this may be minimally important to their allergen city.

Usually, most humans have a low level of circulating IgE antibodies, but some individuals predisposed to developing allergies produce IgE antibodies that are specific for and recognize certain antigens.

Once the allergen is consumed, the individual become sensitized. Sensitization results in production of allergen specific IgE antibodies and cause vasodilation, inflammation, and bronchial constriction. Clinical manifestations vary from urticarial skin reactions to rhinitis and conjunctivitis to asthma and anaphylaxis. The food allergen must be small enough to gain access through the body’s barrier (GI membrane, skin, lungs) but large enough for the immune system to recognize. Food sensitivities can be divided into primary and secondary sensitivities.

Celiac disease or celiac sprue is an example of non-IgE-mediated immunological primary food sensitivity. Celiac disease sufferers are sensitive to glutens, particularly the gliadin fraction of wheat and related crops. Following ingestion of glutens, the absorptive epithelial cells in the small intestine become damaged by an inflammatory process. The intestinal damage results in a severe malabsorption syndrome, i.e., diarrhea, bloating, weight loss, anemia, fatigue, and muscle and bone pain. In children, celiac disease can cause failure to gain weight and growth retardation. Celiac disease is treated by avoiding gliadin foods, which restores the absorptive function and resolves the disease.

Non immunological Primary Food Sensitivities

Last modified: Monday, 26 March 2012, 2:07 PM