Atopy (say "AT-uh-pee") is a predisposition to have allergic reactions. People who have this predisposition are called atopic (say "ay-TOP-ick").
Atopic people often have at least one allergic condition, such as asthma, allergic rhinitis (hay fever), atopic dermatitis, hives or angioedema, or food allergies. The tendency to develop these kinds of allergies runs in families.