Penicillin Allergy De-Labelling: Everything You Need To Know

Picture of Dr Van Nieuwenhuysen
Dr Van Nieuwenhuysen

Dr Christian Van Nieuwenhuysen is an Anaesthetist with additional experience in the investigation of peri-operative drug allergies, including anaphylaxis in response to anaesthetic agents.

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Allergies to medications are serious, and in some cases can be life-threatening. They need to be taken seriously.

But when is an allergy not an allergy? And what can we do when we carry the label of an allergy that we suspect may be incorrect? How can an allergy be “de-labelled”?

What is Penicillin Allergy De-Labelling?

Up to 15% of people in Australia have a penicillin allergy on their medical record, but lots of scientific studies have shown that less than 1% of these people are truly allergic.

This means that their reaction to penicillin was never actually an allergy to begin with, or that so much time has gone by since their reaction that they would be expected to no longer be allergic.

The antibiotic penicillin is part of a large family of antibiotics called “beta-lactams”. Anyone who has a true allergy to a beta-lactam may be “cross-allergic” to any other beta-lactam in the family.

For this reason, a label of penicillin allergy often results in avoidance of all beta-lactam antibiotics by doctors when they have to prescribe antibiotics.

Because beta-lactams are often the best antibiotics for the job, patients with penicillin allergies often end up receiving suboptimal or inappropriate antibiotics to treat infections.

As a result of this, studies have shown that the use of non-beta-lactam antibiotics in Australia is associated with increased hospital days, increased hospital re-admission rates, increased admissions to intensive care, increased bacterial resistance, and increased mortality. 

So, it makes sense to try to identify those patients whose penicillin allergy label may be incorrect or out-of-date, and that’s where the process of “de-labelling” comes in.

Penicillin Allergy De-Labelling

Penicillin allergy de-labelling involves assessing a patient and taking the history of their allergy, performing skin prick tests (allergy testing), and then finally administering a dose of pencilling and observing for a period of time to confirm that no reaction has taken place. 

If no reaction occurs, the de-labelling process is complete, and the patient no longer needs to declare penicillin as an allergy.  Their treating doctors can also be directed to remove penicillin from the patient’s allergy list.

In some cases, where the allergy is deemed to be low risk of being a real allergy, the skin test component can be skipped, and the patient can proceed directly to the “oral drug challenge” step, where they are given the antibiotic dose and observed. This newer method of penicillin allergy de-labelling is cheaper and quicker and can be done in a single appointment.

The process of penicillin allergy de-labelling is so effective that scientific studies have shown that up to 98%  of low to medium risk penicillin allergies can be de-labelled in this way.

Medical professionals should actively encourage their patients to investigate penicillin allergy de-labelling, and patients can assist by raising it with their doctor at the next opportunity.