hy·per·sen·si·tive / ˌhīpərˈsensitiv/ • adj. abnormally or excessively sensitive, either psychologically or in physical response.DERIVATIVES: hy·per·sen·si·tive·ness n.hy·per·sen·si·tiv·i·ty / -ˌsensiˈtivitē/ n.

hypersensitive (hy-per-sen-si-tiv) adj. prone to respond abnormally to the presence of a particular antigen, which may cause a variety of tissue reactions ranging from serum sickness to an allergy (such as hay fever) or, at the severest, to anaphylactic shock (see anaphylaxis). See also allergy, immunity.
—hypersensitivity n.