In psychology, a hypersensitive reaction to an event or stimuli brought about from a previous traumatic event. Exposure to events or circumstances that remind the individual of the previous trauma can result in a similar strong reaction. For example the "flashbacks" of combat veterans.
PSYCHOLOGICAL ANAPHYLAXIS: "Wanting to get low and under cover every time he heard a loud noise was an example of psychological anaphylaxis in my brother. He had done two combat tours in Vietnam."