Allergens from fish and egg.

Allergens from fish and egg belong to some of the most frequent causes of food allergic reactions reported in the literature. Egg allergens have been described in both white and yolk, and the egg white proteins ovomucoid, ovalbumin, ovotransferrin and lysozyme have been adopted in the allergen nomenclature as Gal d1-d4. The most reported allergen from egg yolk seems to be alpha-livitin. In fish, the dominating allergen is the homologues of Gad c1 from cod, formerly described as protein M. A close cross-reactivity exists within different species of fish between this calcium-binding protein family, denominated the parvalbumins. This cross-reactivity has been indicated to be of clinical relevance for several species, since patients with a positive double-blind, placebo-controlled food challenge to cod will also react with other fish species, such as herring, plaice and mackerel. In spite of the importance of these two allergen systems, only a few studies have been performed, and the scarcity of cloned allergens from both of the systems is emphasized.