WordNet (r) 3.0 (2006):

sensitisation
    n 1: the state of being sensitive (as to an antigen) [syn:
         sensitization, sensitisation]
    2: (psychology) the process of becoming highly sensitive to
       specific events or situations (especially emotional events or
       situations) [syn: sensitization, sensitisation]
    3: rendering an organism sensitive to a serum by a series of
       injections [syn: sensitizing, sensitising,
       sensitization, sensitisation]