atopy vs allergy

atopy and allergy both are nouns.

Word	Noun	Adjective	Verb	Adverb
atopy	Yes	No	No	No
allergy	Yes	No	No	No

As nouns, allergy is a hypernym of atopy; that is, allergy is a word with a broader meaning than atopy:

atopy: an allergic reaction that becomes apparent in a sensitized person only minutes after contact
allergy: hypersensitivity reaction to a particular allergen; symptoms can vary greatly in intensity

Other hypernyms of atopy include allergic reaction.

atopy (noun)	allergy (noun)
an allergic reaction that becomes apparent in a sensitized person only minutes after contact	hypersensitivity reaction to a particular allergen; symptoms can vary greatly in intensity