Penicillin and Cephalosporin Allergy

An accurate history is the first and most important step when assessing penicillin allergy or any drug allergy.

Figure 1: Considerations for taking a drug allergy history

Allergy versus Non-allergic Events/Adverse effects:

Many patients can be directly de-labelled through a focussed history alone. A good history helps effectively stratify risk in patients that need immunology assessment (see ‘Referral to an Immunologist’ section).

Penicillin allergy is not an inherited disease. Patients reporting penicillin allergy due to a family history should be directly de-labelled.

Figure 2: Identifying possible allergy and opportuities to de-label

Table 2: Considerations for future antibiotic prescribing and investigations

Figure 2: Identifying possible allergy and opportuities to de-label

Many patients can be directly de-labelled through a focussed history alone. A good history helps effectively stratify risk in patients that need immunology assessment (see ‘Referral to an Immunologist’ section).

Penicillin allergy is not an inherited disease. Patients reporting penicillin allergy due to a family history should be directly de-labelled.'

A simple allergy history (as above, Section 1.1) may allow identification of clearly non-allergic symptoms.

Direct de-labelling is appropriate when the reported symptoms include:

• Nausea or other isolated gastrointestinal symptoms
• Headache
• Mucosal candidiasis
• Patients reporting penicillin allergy due to a family history

In these instances it is appropriate to directly remove the allergy label without need for further assessment. Patients can be told that the history is not in keeping with penicillin allergy and that there is no need for them to avoid penicillins in the future. When de-labelling penicillin allergy, update all healthcare records (e.g. GP, pharmacy, dentist, etc.) and communicate this change to other healthcare providers. Ensure the patient clearly understands the change in their allergy status. It may be useful to communicate this in writing to all parties involved.

When the history suggests:

• Anaphylaxis
• Angioedema
• Acute urticaria temporally related to penicillin administration
• Wheeze/ symptoms suggestive of airway compromise
• Severe cutaneous adverse reactions (SJS, TEN, AGEP, DRESS)
• Haemolytic anaemia, drug-induced cytopaenias, interstitial nephritis, drug-induced liver injury, serum sickness

Patients should be advised to carry personal indicators (e.g. alert jewellery) indicating allergy and avoidance requirements.

Refer to Table 1: Examples of beta lactam antibiotics

At a minimum, drug allergy documentation should contain:

• Drug name
• Signs, symptoms and severity
• Date of occurrence

If the allergy status changes, through review, assessment or testing, update the healthcare records (e.g. GP, hospital, pharmacy, dentist, etc.).

Remove the allergy label and communicate this removal to the patient if:

• the history is inconsistent with allergy or
• the patient has had negative allergy testing.

The following patient groups are prioritised for assessment :

• Patients with an increased antibiotic requirement such as in setting of recurrent infections for any reason
• When there is an absolute requirement for penicillin and other alternatives are not suitable
• Reactions to multiple antibiotics of different classes

Patients with histories that are not in keeping with a true allergic reaction to penicillin do not need to be referred to immunology services or allergy services.

Use of the PENFAST tool is encouraged, in addition to providing a clear history, to assist in referral triage.

Figure 3: PEN-FAST Penicillin Allergy Risk Tool

• Drug allergy assessment – what can a patient expect? The referral will be triaged based on clinical need. Lowest priority referrals will be those sent for assessment without any clear antibiotic requirement. Waiting times for routine referrals may be lengthy as immunology services are constrained by staffing and space.
• An initial assessment of risk will be carried out by taking a drug allergy focussed clinical history. For penicillin allergy referrals this process will be greatly enhanced if a PENFAST score is included in the referral.
• Low risk patients will typically be offered a direct oral challenge with amoxicillin or a similar beta-lactam antibiotic under supervision in an immunology day ward. This process typically takes 1-2 hours.
• Medium/ high risk patients will undergo skin prick testing with a selection of penicillin and beta-lactam medications. If negative this will progress to intradermal testing, where a small amount of the drug is injected into the skin. If these risk management procedures are negative, then an oral challenge will be offered. This entire process can take 3-5 hours.
• It is important that the patient understands that the end point of the testing process is an exposure to (or challenge with) the suspect agent. Referring clinicians should counsel patients about this at the point of referral.
• Penicillin specific IgE tests are widely available, but are poorly sensitive and often uninformative. Their use outside expert settings is not recommended.
• Testing for patients that have had Severe Cutaneous Adverse Reactions (SCAR) remains complex. Often no tests are indicated and the focus is on providing information and optimising future management.

• Patients labelled with a penicillin allergy can safely receive:
  • All non beta-lactam antibiotics (see table 3 below)
  • Cephalosporins if:
    
    • No history of anaphylaxis or other severe reaction to penicillins.
    • The label of allergy is unverified and mild – (eg. historic childhood rash)
• Avoid cephalosporins in patients with a history suggestive of a severe penicillin allergy (anaphylaxis, angioedema, wheezing, temporally related acute urticaria, SCAR) unless specialist testing confirms tolerance.

Table 3: Examples of non-beta-lactam antibiotics

• The incidence of cephalosporin allergy is estimated to be 1–3% of the general population.
• Patients with a cephalosporin allergy label should avoid all cephalosporins unless allergy testing has indicated tolerance of specific cephalosporins.
• Patients labelled with cephalosporin allergy, can receive a penicillin if:
  • There is no history of anaphylaxis or other severe reaction
  • The allergy label is unverified and mild (e.g. historic childhood rash)
• Patients with a cephalosporin allergy can have all non-beta-lactam antibiotics.

Table 3: Examples of non-beta-lactam antibiotics