Guest posting: Professor Jason Trubiano

• Penicillin allergies are not always lifelong. Approximately 50% are lost over five years and 80% at 10 years.
• A reaction to penicillin, typically a benign rash during a childhood, is unlikely to be a true allergy, with more than 97% negative on allergy testing.
• Only 1–2% of patients with a confirmed penicillin allergy have an allergy to cephalosporins. Non-cross reactive cephalosporins can be administered to a patient with any penicillin allergy phenotype, except a severe delayed reaction (e.g. blistering or mucosal involvement rash).  See Betalactam cross reaction matrix below.
• Patients with a low-risk history of penicillin allergy (e.g. benign childhood rash, delayed non-severe rash > 5 years ago) can proceed to a direct oral challenge (i.e. test dose) without prior skin testing.
• A low-risk penicillin allergy can be ascertained by utilising an internationally validated risk assessment score – PEN-FAST. A score of < 3 is associated with a 96% change of a negative test.
• In many cases, with appropriate assessment and allergy testing, it may be possible to remove the penicillin allergy label and avoid the negative health consequences of such a “label”.

References

• Devchand M and Trubiano J.  Australian Prescriber, December 2019: 42 : 192-99. 
• Copaescu et al. JAMA Internal Medicine. 2023 Sep 1;183(9):944-952.
• PEN-FAST risk assessment tool: qxmd.com/calculate/calculator_752/pen-fast-penicillin-allergy-risk-tool

Professor Trubiano is an Infectious Diseases Physician and Director of Infectious Diseases at Austin Health. He is an NHMRC Emerging Leadership Fellow at the University of Melbourne, Department of Infectious Diseases. He is the laboratory head for the Centre for Antibiotic Allergy and Research (Austin Health) and his research explores health services programs for antibiotic allergy and novel diagnostics and pharmacogenomic predictors for severe T-cell mediated drug reactions.

Betalactam cross reaction matrix