hyperreactor
/ˌhaɪpərriˈæktər/
noun
- A person or thing that reacts excessively or very strongly to a stimulus.
- As a known hyperreactor to bee stings, she always carried an epinephrine injector.
- In the experiment, the hyperreactor mice showed extreme responses to mild stress.
- The coach called him a hyperreactor because he got angry at every minor foul.