urtication vs skin rash

urtication and skin rash both are nouns.

Word	Noun	Adjective	Verb	Adverb
urtication	Yes	No	No	No
skin rash	Yes	No	No	No

As nouns, skin rash is a hypernym of urtication; that is, skin rash is a word with a broader meaning than urtication:

urtication: 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
skin rash: any red eruption of the skin

Other hypernyms of urtication include efflorescence, rash, roseola, hypersensitivity reaction.

urtication (noun)	skin rash (noun)
a sensation of having been stung by nettles	any red eruption of the skin
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