cluster headache vs histamine headache

cluster headache and histamine headache both are nouns.

Word	Noun	Adjective	Verb	Adverb
cluster headache	Yes	No	No	No
histamine headache	Yes	No	No	No

As nouns, cluster headache and histamine headache are synonyms defined as:

cluster headache and histamine headache: a painful recurring headache associated with the release of histamine from cells

cluster headache (noun)	histamine headache (noun)
a painful recurring headache associated with the release of histamine from cells	a painful recurring headache associated with the release of histamine from cells