'Cephalosporin allergy' label is misleading

Penicillins and cephalosporins can cause a similar spectrum of allergic reactions at a similar rate. Cross-reactive allergy between penicillins and cephalosporins is rare, as is cross-reaction within the cephalosporin group. Patients should therefore not be labelled ‘cephalosporin-allergic’. Cross-reactive allergy may occur between cephalosporins (and penicillins) which share similar side chains. Generally, a history of a penicillin allergy should not rule out the use of cephalosporins, and a history of a specific cephalosporin allergy should not rule out the use of other cephalosporins. Specialist advice or further investigations may be required when the index reaction was anaphylaxis or a severe cutaneous adverse reaction, or when the antibiotics in question share common side chains. When recording a drug allergy in the patient’s records, it is important to identify the specific drug suspected (or confirmed), along with the date and nature of the adverse reaction. Records need to be updated after a negative drug challenge.