sickening vs nauseous

sickening and nauseous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
sickening	No	Yes	No	No
nauseous	No	Yes	No	No

As adjectives, sickening and nauseous are synonyms defined as:

Other synonyms of sickening include loathsome, nauseating, noisome, offensive, queasy, vile.

sickening (adjective)	nauseous (adjective)
causing or able to cause nausea	feeling nausea; feeling about to vomit
	causing or able to cause nausea