hypersensitivity; oversensitivity
Medical term for an exaggerated immune response or heightened sensitivity to stimuli. Also used in non-medical contexts for emotional or sensory oversensitivity.
Hay fever is a type of hypersensitivity.
He suffers from multiple chemical sensitivity.
Compound of 過敏 (kabin, 'oversensitive') + 症 (shō, 'condition' or 'symptom'). The exact historical derivation is uncertain, but the kanji components transparently convey the meaning.