Penicillin allergy

Children with pneumonia with a label of penicillin allergy were found to have:

  • higher risk of hospitalization (RR 1.15)
  • acute respiratory failure (RR 1.27)
  • and need for intensive care (RR 1.46; 95% CI, 1.15-1.84)
  • increased cutaneous drug reactions (RR 2.43)

[US Journal of Allergy & Clinical Immunology in Practice.  11(6):1899-1906.e2, 2023 Jun.]


Atanaskovic-Markovic et al found that cross-reactivity between cephalosporins and penicillins varied between 0.3 and 23.9%, being higher among penicillins and between first-generation and second-generation cephalosporins.

However, it has recently been shown that all penicillin allergic children can tolerate cefuroxime, presumably as it has a different side chain.

Cross-reactivity appears to be higher in immediate reactions, and when penicillins and cephalosporins are identical or similar in the R1 side chain, as happens with the first and second-generation cephalosporins.

Currently BNFc says to avoid cefalosporins if history of immediate penicillin hypersensitivity, but if use of cefalosporin is “essential” then can be used (but not cefalexin!).

Canadian study did oral challenges for non-blistering rashes – safe – but mostly cefprozil allergy (and linked to food allergies).


In hypothetical case of de-labelled patient, 47% of anaesthetists would not prescribe penicillin to patient anyway (n=5000)!

Primary care don’t always remove label even after de-labelling! (patient held records would help…)

Needs culture change in primary care and paeds of documenting reactions!

Make sure note is added to patient record when de-labelled. Electronic labels don’t necessarily help – not always possible to remove an allergy label from drug prescription system, depending on the system, may only allow subsequent note to be added.  Free text systems do not encourage accurate description!

Alabama trial from NIHR to report on RCT of de-labelling in primary care; SPACE study in secondary care (nurse/pharmacist delivered).

See Testing for antibiotic allergy.