unhealthiness vs ill health

unhealthiness and ill health both are nouns.

Word	Noun	Adjective	Verb	Adverb
unhealthiness	Yes	No	No	No
ill health	Yes	No	No	No

As nouns, unhealthiness and ill health are synonyms defined as:

unhealthiness and ill health: a state in which you are unable to function normally and without pain

Other synonyms of unhealthiness include health problem.

unhealthiness (noun)	ill health (noun)
a state in which you are unable to function normally and without pain	a state in which you are unable to function normally and without pain