sensitization

noun

1. the state or process of being sensitized.
2. Psychology. the process of becoming susceptible to a given stimulus that previously had no effect or significance.
3. Immunology.
   1. a state or condition in which a previously encountered foreign substance triggers an immune reaction.
   2. an immunologic state or condition that is evidenced by the acquired ability of a cell or individual to detect the presence of a foreign substance upon reexposure to the substance and to react immunologically.

n.1862, originally in photography, noun of action from sensitize. n.

1. The act or process of inducing an acquired sensitivity or allergy.