Penicillin allergy is commonly reported, but 9 out of 10 times, penicillin will be tolerated if administered
About 10% of people report a penicillin allergy, but 90%–95% of those individuals are not truly allergic.1 Reasons for this include mislabelling intolerances as allergies and waning of immunoglobulin E–mediated allergy over time.2,3
The label of penicillin allergy is bad for patients and the health care system
More than just a problem for prescribers of antibiotics, the label of penicillin allergy is associated with the use of costly and less effective second-line and broad-spectrum antibiotics,1–3 a 55% increased risk of acquiring methicillin-resistant Staphylococcus aureus, and a 35% increased risk of Clostridium difficile infection (Appendix 1, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.181117/-/DC1).4
Patients reporting penicillin allergy can be easily risk stratified to determine whether they require specialist evaluation
A known adverse effect of a penicillin (e.g., nausea) should not be documented as an allergy; likewise, avoidance of penicillin is unnecessary in those with a family history of penicillin allergy without a personal history of one, or in those who have since tolerated penicillin (low-risk). In those who have experienced severe delayed hypersensitivity reactions such as drug reaction with eosinophilia and systemic symptoms or Stevens–Johnson syndrome and toxic epidermal necrolysis (high-risk), β-lactams should be strictly avoided; allergy skin testing is contraindicated. Patients reporting probable or unclear immunoglobulin E reactions that may present as rapid-onset urticaria, angioedema or anaphylaxis (intermediate risk) should be referred (Appendix 1).2,3
Penicillin allergy is lost over time, with resolution in 80% of people over 10 years, and in 50% over 5 years
Those with remote (> 10 yr) reactions are unlikely to still be allergic and should be tested before challenge with penicillin.1–3 If there is an acute indication for antibiotics, expert consultation is preferable to guide testing versus empiric therapy.
Allergy referral and testing is vastly underused, but is safe, accurate, rapid and cost-effective
Allergy testing over 1–2 hours using a combination of skin and challenge testing by trained personnel has been shown to be safe and effective for children, adults, inpatients and outpatients, with a negative predictive value close to 100%.1–3
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Footnotes
CMAJ Podcasts: author interview at https://soundcloud.com/cmajpodcasts/181117-five
Competing interests: None declared.
This article has been peer reviewed.
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- Penicillin allergy is commonly reported, but 9 out of 10 times, penicillin will be tolerated if administered
- The label of penicillin allergy is bad for patients and the health care system
- Patients reporting penicillin allergy can be easily risk stratified to determine whether they require specialist evaluation
- Penicillin allergy is lost over time, with resolution in 80% of people over 10 years, and in 50% over 5 years
- Allergy referral and testing is vastly underused, but is safe, accurate, rapid and cost-effective
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