Penicillin allergy and de-labelling

Approximately 10% of people identify as having a penicillin allergy, however true penicillin allergy is estimated to affect only one percent of the population.²⁶⁸ Symptoms of allergy can range from mild itch to severe and life-threatening anaphylaxis. If an adverse reaction to penicillin is suspected, it is critical that a clear account is obtained and documented.

Allergy can be defined by type:

Type I reaction (usually within one hour of administration):

• itchy rash
• facial/throat swelling
• breathing difficulties
• collapse

Type IV reaction (delayed reactions and usually occur 24-72 hours after administration):

• rash with blistering
• oral or genital ulceration or blistering
• rash associated with a severe systemic illness requiring admission to hospital

If an individual experiences type I or type IV reactions, it is an absolute contra-indication to further prescriptions.

The following should be considered as adverse reactions, but not allergic reaction:

• nausea and vomiting
• diarrhoea
• abdominal pain

As a result of an incorrect penicillin allergy label, individuals may receive alternative, less effective antibiotics, or antibiotics that are more likely to be associated with adverse effects or increased risk of antimicrobial resistance (AMR).²⁶⁹

This topic describes penicillin allergy and the process of de-labelling this allergy where appropriate.

Antibiotics are commonly prescribed medicines essential for the treatment and prevention of bacterial infections. More than 83% of antibiotics are prescribed in a primary care setting²⁷⁰ and at any one time approximately one in three patients in hospital receive an antibiotic. Penicillin antibiotics are highly effective and are the preferred first line treatment in many bacterial infections.

AMR arises when micro-organisms, such as bacteria, develop the ability to withstand antimicrobial treatments making infections harder to treat. AMR is associated with more severe disease and higher mortality.²⁶⁹ To slow resistance development it is important to ensure antibiotics are prescribed appropriately and use the narrowest spectrum antibiotic which will be effective.

A penicillin allergy label is associated with:^271,272

• increased morbidity (side effects, and drug interactions)
• greater healthcare costs due to longer hospital stays, increased readmission rates, and more critical care admissions
• increased risk of post-surgical wound infections
• increased risk of reactions pre-operatively (to teicoplanin)
• increased rates of methicillin resistant Staphylococcus aureus (MRSA), Clostridioides difficile (C. diff), and vancomycin-resistant Enterococcus (VRE) infection.

This is most likely through use of broad-spectrum alternatives rather than ‘best first-line’ antimicrobial therapy.

It is essential therefore that individuals who have a potentially incorrect penicillin allergy label are fully assessed to confirm if they are truly allergic or not.

To determine whether an individual has a penicillin allergy, consider description of the reaction:

• which antibiotic did the reaction occur with?
• did this reaction result in hospitalisation or was emergency treatment required?
• if a rash was present, then
  • describe the rash
  • could it be related to an underlying condition, e.g. viral?
  • how long after administration did the rash appear?
• how long after administration did the reaction occur? Note reactions can be immediate or up to 30 days afterwards
• how long ago did the adverse reaction occur?
• what was the route of administration?
• did the reaction resolve on stopping the antibiotic? If so, what happened after stopping the drug?
• have they tolerated penicillin-based antibiotics (e.g. amoxicillin) since the initial recorded reaction?

If an individual had a reaction to an antibiotic, including penicillin, document:

• the antibiotic and route administered (e.g. oral or intravenous)
• a description of reaction (timing and symptoms/signs)
• how quickly the reaction resolved

Recording this information can help decision-making if the individual requires antibiotics in the future.

People with a type I or type IV reaction should carry an allergy card²⁷³ to prevent inadvertent prescribing of a penicillin containing antibiotic, which contains the following information:

Front of penicillin allergy card

Reverse of penicillin allergy card

People with a true penicillin allergy should avoid antibiotics with a similar structure (beta-lactam ring) e.g. cephalosporins, carbapenems unless on specialist advice.

If an individual experiences a true penicillin allergy the antibiotic should be stopped immediately.

People with anaphylaxis should be treated as an emergency (see resource from Resuscitation Council UK).

Supporting people through reduction and ongoing review of medication

For people who do not have a true penicillin allergy, it may be possible to consider supervised penicillin allergy de-labelling (PADL) oral challenge. PADL may be undertaken in a hospital setting after careful assessment of risk.

In circumstances where there is a very low probability of a penicillin allergy:

• the ‘allergy’ occurred more than 10 years ago and symptoms were poorly recalled
• were non-severe or GI in nature
• there were no symptoms to suggest type I (anaphylaxis) or type IV hypersensitivity

Following consent, individuals receive a supervised low dose of penicillin by personnel trained in anaphylaxis management and resuscitation and are closely monitored for one hour for signs of reaction.

PADL is a well-established process and is supported by national and international allergy groups and evaluated by the Scottish Antimicrobial Prescribing Group (SAPG).²⁷³

Performing PADL in primary care is not currently recommended. Access to PADL from primary care currently varies across Scotland and local referral routes, where developed, should be followed.

Does the person understand the outcomes of the review, including risk and benefits?

• The nature of penicillin allergy should be discussed and clarified with the person to optimise future care and reduce risk of adverse effects to non-penicillin antibiotics (if non-allergic), and allergic reactions, if true allergy.
• If there is not a true penicillin allergy, the risk of a less appropriate antibiotic being used.
• By removing a penicillin allergy label, does the individual understand that they can take penicillin-based antibiotics in the future?

Agree the plan

• The nature of the allergy or details of the allergy de-labelling should be recorded in the individual’s medical records and shared with primary care, health care professionals and family involved in their care.

• self-management/support tools
• decision aids

The SAPG has developed a penicillin allergy de-labelling pathway and toolkit for use in secondary care. The toolkit includes information and resources to support individuals.