Elimination of iron pigments and background staining which mask immunoperoxidase reactions

When immunohistochemical stainings are applied to demonstration of antigens in histopathological specimens, the ferrous pigments which may be present in the tissues usually mask the final precipitates of the reaction. These pigments can be eliminated with oxalic acid or sodium dithionite after the immunohistochemical staining. These treatments also help in the bleaching of unspecific background stain.