Complete doctor's desk guide to routine pathology tests.

An allergy is a hypersensitivity reaction initiated by the immune system. Allergy can be antibody- or cell mediated. The antibody typically responsible for an allergic reaction belongs to the IgE isotype, and these individuals may be referred to as suffering from an IgE-mediated allergy. Individuals suffering from a cell-mediated allergy are referred to as suffering from a non-IgE mediated allergy.

Reactions not initiated by the immune system are not allergy and cannot be detected by allergy tests. Examples of these are lactose intolerance, sensitivity to caffeine and other intolerances.