FOOD ALLERGENS

A food allergen may be defined as a substance that reacts with IgE ant ibodies, induces allergic sensitisation or induces allergic reactions. Some allergens only induce allergic sensitisation but do not provoke symptoms, while others bind IgE but do not induce mast cell degranulat ion. There is no common structure that can predict whether a given ant igen may be a strong food allergen. A complete food allergen, e.g. fis h parvalbumin, is capable of stimulating the immune system to produce IgE antibodies, and degranulate mast cells upon subsequent contact. Th e reason(s) for why some patients with IgE to ovalbumin tolerate eggs, and why some react on one occasion but not on another, are mostly unc lear, but may be related to changes in gut permeability induced by oth er food substances or by gastro-intestinal inflammation prior to the a llergen contact. IgE antibodies to fruit or vegetables often show cros s-reactivity, due to carbohydrate structures. These cross-reactive gly cans have been designated cross-reactive carbohydrate determinants (CC D). Anti-CCD antibodies are highly cross-reactive. The antibodies do n ot have clinical significant because CCD-containing foods are usually well-tolerated by patients with IgE antibodies to CCD. These IgE antib odies may cause confusion in relation to allergy diagnosis. (C) 1997 E lsevier Science B.V.