pollinosis vs hay fever

pollinosis and hay fever both are nouns.

Word	Noun	Adjective	Verb	Adverb
pollinosis	Yes	No	No	No
hay fever	Yes	No	No	No

As nouns, pollinosis and hay fever are synonyms defined as:

pollinosis and hay fever: a seasonal rhinitis resulting from an allergic reaction to pollen

pollinosis (noun)	hay fever (noun)
a seasonal rhinitis resulting from an allergic reaction to pollen	a seasonal rhinitis resulting from an allergic reaction to pollen