[Pseudo-allergic drug reactions: pathophysiology and diagnosis]

The symptomatology of allergic diseases may be imitated by non-immunological, so-called "pseudo-allergic" reactions. Phenocopies of any type of allergic reaction may occur. Pseudo-allergic drug reactions may be caused by the active components as well as by additives. Anaphylactoid pseudo-allergic reactions are of special clinical interest. Their pathomechanism has not been conclusively elucidated yet. Based on clinical and experimental data, we discuss some hypothetic mechanisms of a few compounds, always keeping in mind the possibility of allergic mechanisms not yet identified. For the diagnosis of pseudo-allergic drug reactions we need provocation tests, as skin tests are not possible, and routine in-vitro assays are not available.