1) excessively or abnormally sensitive
2) abnormally susceptible physiologically to a specific agent (as a drug or antigen)
hy·per·sen·si·tive·ness n
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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). It is thought that when the normal antigen-antibody defence reaction is followed by tissue damage this may be due to an abnormality in the working of the complement system. See also allergy, immunity.
• hypersensitivity n.
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hy·per·sen·si·tive (hi″pər-senґsĭ-tiv) 1. having abnormally increased sensitivity. 2. reacting with characteristic signs and symptoms to the application of or contact with certain substances (allergens) in amounts that are innocuous to nonsensitized individuals. See hypersensitivity.Medical dictionary. 2011.