hyper == excess of energy or enthusiasm
sensitivity == capacity to perceive using the senses
A characteristic used (particularly in medicine) to describe one's excessive responsiveness to stimuli. A person can exhibit hypersensitivity to things like light and sound, drugs, temperature, etc.
Because her eyes were infected, Mary exhibited hypersensitivy to light.
Can also be used to describe an emotional state wherein one is easily upset or disturbed.
John's hypersensitivity stems from his recent divorce.
The term "hypersensitivity disease" or "hypersensitivity disorder" refers to diseases that create allergic reactions and other immune responses to outside agents and pollutants that are harmful to the patient.