dermatitis vs eczema

dermatitis and eczema both are nouns.

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

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

dermatitis: inflammation of the skin; skin becomes itchy and may develop blisters
eczema: generic term for inflammatory conditions of the skin; particularly with vesiculation in the acute stages

dermatitis (noun)	eczema (noun)
inflammation of the skin; skin becomes itchy and may develop blisters	generic term for inflammatory conditions of the skin; particularly with vesiculation in the acute stages