atopy
(at'ŏ-pē 
)
[Gr. atopia, strangeness]
A type I hypersensitivity or allergic reaction for which there is a genetic predisposition. Normal allergic reactions are not genetically determined. The basis for atopy lies in the histocompatibility genes. The child of two parents with atopic allergy has a 75% chance of developing similar symptoms; if one parent is affected, the child has a 50% chance of developing atopy. Hay fever and asthma are two of the most commonly inherited allergies; contact dermatitis and gastrointestinal reactions also may be inherited. As with all type I hypersensitivity reactions, IgE is the primary antibody involved. Atopy is often associated with asthma.
SYN: atopic allergy.