Adverse Drug Reactions and Allergies

An adverse drug reaction is any undesired or unintended consequence that occurs when a drug is given as appropriate treatment for a condition

In contrast, an allergy is a reproducible hypersensitivity reaction initiated by a specific immunological mechanism, referring to either IgE or T-cell mediated reactions

A label of allergy to penicillin is concerning, and, in adults (who may have been labelled as children), has been shown to delay treatment in emergency settings, causes prolonged stays in hospital, and worse outcomes while in hospital. The antibiotics that often replace penicillin are typically more expensive, have worse side effects and can contribute to resistance and C. difficile

Penicillin allergies are not genetic, and a family history of penicillin allergy should not be used to label an individual as allergic