urticaria vs efflorescence

urticaria and efflorescence both are nouns.

Word	Noun	Adjective	Verb	Adverb
urticaria	Yes	No	No	No
efflorescence	Yes	No	No	No

As nouns, efflorescence is a hypernym of urticaria; that is, efflorescence is a word with a broader meaning than urticaria:

urticaria: an itchy skin eruption characterized by weals with pale interiors and well-defined red margins; usually the result of an allergic response to insect bites or food or drugs
efflorescence: any red eruption of the skin

Other hypernyms of urticaria include rash, roseola, skin rash, hypersensitivity reaction.

urticaria (noun)	efflorescence (noun)
an itchy skin eruption characterized by weals with pale interiors and well-defined red margins; usually the result of an allergic response to insect bites or food or drugs	a powdery deposit on a surface
	the time and process of budding and unfolding of blossoms
	any red eruption of the skin
	the period of greatest prosperity or productivity