flare up vs intensify

flare up and intensify both are verbs.

Word	Noun	Adjective	Verb	Adverb
flare up	No	No	Yes	No
intensify	No	No	Yes	No

As verbs, intensify is a hypernym of flare up; that is, intensify is a word with a broader meaning than flare up:

Other hypernyms of flare up include deepen.

flare up (verb)	intensify (verb)
erupt or intensify suddenly	become more intense
ignite quickly and suddenly, especially after having died down	make more intense, stronger, or more marked
	increase in extent or intensity
	make the chemically affected part of (a negative) denser or more opaque in order produce a stronger contrast between light and dark