Immunological reactions to non-virus substances of vaccines may be of considerable significance to the pathogenesis of neurological complications after anti-influenza vaccination. A 60 year old female patient with a known allergic diathesis developed a meningoencephalitis syndrome a few hours after vaccination. The case history as well as the clinical course suggested an immunopathogenetic mechanism. We therefore analyzed the immune profile. Intracutaneous testing with chicken meat and chicken egg protein lead to a striking local anaphylactic reaction which is discussed in causal relation to the postvaccination complication.