Provided are: a novel egg allergy antigen a diagnosis method and a diagnosis kit for egg allergy a medicinal composition comprising the antigen an egg from which the antigen is eliminated or in which the antigen is reduced, a processed egg product, or a bird laying the egg or hatched from the egg a method for producing a processed egg product from which the antigen is eliminated or in which the antigen is reduced and a tester for determining the presence or absence of an egg antigen in a subject.