Definitions
1.nounA disorder of the immune system causing adverse reactions to substances (allergens) not harmful to most and marked by the body's production of histamines and associated with atopy, anaphylaxis, and asthma.
2.nounAny condition of hypersensitivity to a substance.
3.nounAltered susceptibility to a first treatment as exhibited in reaction to a subsequent one.
4.nounAn antipathy, as toward a person or activity.