Bird-egg syndrome. Cross-reactivity between bird antigens and egg-yolk livetins in IgE-mediated hypersensitivity

87 adult patients from our allergy clinic were skin tested with budgerigar and canary feathers, hen's egg white and egg yolk and common inhalant allergens. Of 59 patients found to be atopic, 17 (29%) were concomitantly sensitized to bird dander and egg proteins, 10 of them being symptomatic to bird dander and/or egg exposure. All but 1 of the egg-symptomatic patients were exposed to pet birds. The patients with strong serological reactivity to bird antigens were also exclusively sensitized to egg proteins, in particular to livetins (water-soluble fractions of egg-yolk proteins). Extensive RAST-inhibition studies demonstrated identical patterns of cross-reactivity between bird dander and hen's egg proteins, livetins being the major cross-reacting antigens. This peculiar IgE-mediated allergy is designated as 'bird-egg syndrome'. It is suggested that egg intolerance in adults is mainly due to sensitization to egg-yolk livetins and can be provoked by inhalation of pet bird dander. Thus, it must be distinguished from the common egg-white allergy of atopic children. Our study further underlines the importance of respiratory sensitization in adult food allergy. On the other hand, exposure to cross-reacting antigens by ingestion might also influence the allergic manifestations to inhalant allergens.