na-adjective, noun
oversensitivity; nervousness; hypersensitivity
Describes a state of being excessively sensitive or reactive, often to stimuli, criticism, or social situations. Can be used medically or psychologically.
彼は批判に過敏で、すぐに落ち込んでしまう。
He is oversensitive to criticism and gets depressed easily.
この薬は皮膚が過敏な人には使え
This medicine cannot be used by people with hypersensitive skin.
敏感 means 'sensitive' in a neutral or positive sense, while 過敏 implies excessive, often problematic sensitivity.
Formed from 過 (excess) and 敏 (sensitive, quick). The combination straightforwardly yields 'excessive sensitivity'.