Abstract: Described is an antibody, or a fragment of an antibody, which binds to an epitope under specifically chosen conditions, and the binding of which to that epitope is broken under specifically chosen different conditions, in addition to an antibody or fragment thereof with which a diagnostically, therapeutically or cosmetically active substance is optionally conjugated, for targeted and temporary diagnostic, therapeutic or cosmetic treatment of externally accessible parts of the human and animal body, wherein both the specifically chosen binding conditions and the conditions wherein the binding is broken lie within physiologically acceptable limits and are formed by the pH and/or ionic strength.