Beta-lactam hypersensitivity is the most common reported antibiotic allergy, but studies show that while 20% of hospital patients carry an allergy labels in America, only 1 in 20 have proven IgE-mediated allergy necessitating avoidance. This presentation talks about the structure of Beta-lactam and its importance when considering hypersensitivity. Prof Peter presents information on incorrect labelling of patients in the context of antibiotic stewardship and states that over last 5 to 8 years many studies to show that patients carrying incorrect penicillin allergy labels cost much more and have to 5 times increased risk of adverse drug reactions to other drugs prescribed. Peter also discusses the assessment of individual patients in the context of the spectrum of reactions and risk factors and talks about testing methods and the setting for testing. Prof Peters ends the presentation by discussing a case study of a true allergy which requires treatment in the in the context of pregnancy with syphilis.