itchiness vs itching

itchiness and itching both are nouns.

Word	Noun	Adjective	Verb	Adverb
itchiness	Yes	No	No	No
itching	Yes	No	No	No

As nouns, itchiness and itching are synonyms defined as:

itchiness and itching: an irritating cutaneous sensation that produces a desire to scratch

Other synonyms of itchiness include itch.

itchiness (noun)	itching (noun)
an irritating cutaneous sensation that produces a desire to scratch	an irritating cutaneous sensation that produces a desire to scratch