heat rash vs prickly heat

heat rash and prickly heat both are nouns.

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

As nouns, heat rash and prickly heat are synonyms defined as:

heat rash and prickly heat: obstruction of the sweat ducts during high heat and humidity

Other synonyms of heat rash include miliaria.

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