atopic eczema vs dermatitis

atopic eczema and dermatitis both are nouns.

Word	Noun	Adjective	Verb	Adverb
atopic eczema	Yes	No	No	No
dermatitis	Yes	No	No	No

As nouns, dermatitis is a hypernym of atopic eczema; that is, dermatitis is a word with a broader meaning than atopic eczema:

atopic eczema: a severe form of dermatitis characterized by atopy
dermatitis: inflammation of the skin; skin becomes itchy and may develop blisters

atopic eczema (noun)	dermatitis (noun)
a severe form of dermatitis characterized by atopy	inflammation of the skin; skin becomes itchy and may develop blisters