heat rash vs efflorescence

heat rash and efflorescence both are nouns.

Word	Noun	Adjective	Verb	Adverb
heat rash	Yes	No	No	No
efflorescence	Yes	No	No	No

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

Other hypernyms of heat rash include rash, roseola, skin rash.

heat rash (noun)	efflorescence (noun)
obstruction of the sweat ducts during high heat and humidity	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