swimmer's itch vs dermatitis

swimmer's itch and dermatitis both are nouns.

Word	Noun	Adjective	Verb	Adverb
swimmer's itch	Yes	No	No	No
dermatitis	Yes	No	No	No

As nouns, dermatitis is a hypernym of swimmer's itch; that is, dermatitis is a word with a broader meaning than swimmer's itch:

swimmer's itch: a sensitization reaction to repeated invasion of the skin by cercariae of schistosomes
dermatitis: inflammation of the skin; skin becomes itchy and may develop blisters

swimmer's itch (noun)	dermatitis (noun)
a sensitization reaction to repeated invasion of the skin by cercariae of schistosomes	inflammation of the skin; skin becomes itchy and may develop blisters