Referring to a person who reacts more strongly than usual to an antigen.
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. It is thought that when the normal antigen-antibody defense reaction is followed by tissue damage this may be due to an abnormality in the working of the complement system.
Excessively and abnormally susceptible to a stimulus (e.g., an antigen like pollen).