bleaching agent vs whitener

bleaching agent and whitener both are nouns.

Word	Noun	Adjective	Verb	Adverb
bleaching agent	Yes	No	No	No
whitener	Yes	No	No	No

As nouns, bleaching agent and whitener are synonyms defined as:

bleaching agent and whitener: an agent that makes things white or colorless

Other synonyms of bleaching agent include blanching agent, bleach.

bleaching agent (noun)	whitener (noun)
an agent that makes things white or colorless	an agent that makes things white or colorless