The Process Of Penicillin Allergy De-Labelling

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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Many people have been told at some stage that they are allergic to penicillin, but were never truly allergic. The “label” of penicillin allergy has been shown to lead to poorer health outcomes for the patient, some of which can be life-threatening. Queensland Anaesthetic Reaction Clinic can help “de-label” you, but what is The Process Of Penicillin Allergy De-Labelling?

How Does Penicillin Allergy De-Labelling Work?

The Benefits of Penicillin De-Labelling are well established. Avoiding penicillin and it’s related antibiotics means that inferior antibiotics are often used to treat infection. The use of inferior antibiotics in Australia to treat infection has been associated with longer hospital stays, increased rates of re-admission with infection, increased chance of needing ICU, increased antibiotic resistance in bacteria, and increased risk of dying from infection.

Penicillin Allergy De-Labelling is the process of evaluating and disproving a label of penicillin allergy.

Until recently, this process was lengthy and often required multiple appointments. A patient would need to be assessed with a consultation, brought back for allergy testing (“skin testing” and then potentially brought back again for an oral drug challenge.

Oral drug challenge is the final and most important step in the Process of Penicillin Allergy De-Labelling. What does this involve? When we have a patient who we believe to be non-allergic to penicillin, we administer a tablet of penicillin in a medically supervised environment, observe for at least an hour, and then remove the allergy from the patients allergy list if no reaction occurs. The most important types of allergic reactions occur very rapidly after exposure, so if this observation period is uneventful, it effectively guarantees that anaphylaxis will not occur. 

In the past, we used to routinely perform skin testing (skin pricks) before progressing to oral antibiotic challenge. Skin testing is time-consuming and potentially expensive for patients, and often requires a whole appointment on its own. If a skin test was negative, we would proceed to oral challenge because we would be confident that the risk of a reaction was low. If skin testing was positive, we would not proceed to oral challenge, and we would keep the penicillin allergy label.


Fortunately, we now have screening tools that allow us to determine which patients are low-risk for their allergy being serious, without needing skin testing. That means that in a single appointment, we can see a patient, assess their risk, and proceed directly to oral antibiotic challenge if their risk of a reaction is low. This process is called “direct oral challenge”, because it bypasses skin testing and goes directly to oral challenge.

Recent studies have shown that this process is extremely safe, saves both time and patient expense, and that 98% of patients assessed as low-medium risk can be quickly and safely delabelled of their penicillin allergy in this way.

Patients who are assessed as high-risk for their allergy being serious will need to have skin testing first to ensure safety, but this represents only a small number of patients with a penicillin allergy. The vast majority can safely proceed to direct oral challenge under supervision.

Hopefully this short article has helped to answer the question “How Does Penicillin Allergy De-labelling Work?

Queensland Anaesthetic Reaction Clinic offers Penicillin Allergy De-labelling in Brisbane through our clinic rooms based at Greenslopes Private Hospital. This can usually be done in a single appointment. Discuss the Benefits of Penicillin De-labelling with your GP or other specialist at the next opportunity!