In rare cases, you may notice any of the following side effects after administration of KOGENATE Bayer 250 IU: • rash/ itchy rash, local reactions at the injection site (e. g. burning sensation, temporary redness) • hypersensitivity reactions (e. g. tightness of the chest/ general feeling of being unwell, dizziness and nausea and mildly reduced blood pressure, which may make you feel faint upon standing) • unusual taste in the mouth • fever.