histamine headache vs cluster headache

histamine headache and cluster headache both are nouns.

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

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

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

histamine headache (noun)	cluster 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