The present invention provides: a novel antigen for allergies to fish; a diagnostic method and diagnostic kit for allergies to fish; a pharmaceutical composition that includes the antigen; fish and fish eggs from which the antigen has been removed, a processed product that comprises said fish or fish eggs, or fish that produce or are born from said fish eggs; and a tester for determining whether a fish antigen is present in a target object. The present invention also relates to: a polypeptide that includes an epitope for an antigen; an allergy diagnostic kit, diagnostic composition, and diagnostic method that include the polypeptide; a pharmaceutical composition that includes the polypeptide; and a raw material or processed product from which antigens that include the polypeptide have been removed or in which the amount of said antigens has been reduced. The present invention also relates to a tester for determining whether an antigen is present in a target object.
