annoying vs irritation

annoying and irritation both are nouns.

Word	Noun	Adjective	Verb	Adverb
annoying	Yes	Yes	No	No
irritation	Yes	No	No	No

As nouns, annoying and irritation are synonyms defined as:

Other synonyms of annoying include annoyance, vexation.

annoying (noun)	irritation (noun)
the act of troubling or annoying someone	unfriendly behavior that causes anger or resentment
	the act of troubling or annoying someone
	an uncomfortable feeling of mental painfulness or distress
	a sudden outburst of anger
	the psychological state of being irritated or annoyed
	the neural or electrical arousal of an organ or muscle or gland
	(pathology) abnormal sensitivity to stimulation

annoying (adjective)	irritation (adjective)
causing irritation or annoyance