sensitization has 3 distinct synonyms spread across 3 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the state of being sensitive (as to an antigen)
(psychology) the process of becoming highly sensitive to specific events or situations (especially emotional events or situations)
rendering an organism sensitive to a serum by a series of injections
Synonyms, antonyms and the broader and narrower relations for sensitization come from Princeton University’s WordNet. Full sources and licences.