bulla vs blister

bulla and blister both are nouns.

Word	Noun	Adjective	Verb	Adverb
bulla	Yes	No	No	No
blister	Yes	No	Yes	No

As nouns, bulla and blister are synonyms defined as:

bulla and blister: (pathology) an elevation of the skin filled with serous fluid

Other synonyms of bulla include bleb.

bulla (noun)	blister (noun)
the round leaden seal affixed to a papal bull	(pathology) an elevation of the skin filled with serous fluid
(pathology) an elevation of the skin filled with serous fluid	(botany) a swelling on a plant similar to that on the skin
	a flaw on a surface resulting when an applied substance does not adhere (as an air bubble in a coat of paint)