PEM PEarl: Antibiotic hypersensitivity 

This 2022 review serves as an update to the 2010 guidelines for antibiotic cross-reactivity and hypersensitivity. There are a few charts/diagrams that are clinically relevant to us in the PED included below. Here are some additional specific details:

• cephalosporin allergies are likely directed at the R-group side chain, not the Beta-lactam core.
• cross reactivity is highest among Beta-lactams that share an R1-group side chain
• About 2% of patients with verified penicillin allergy will react to cephalosporins

Bottom Line: With a history of non-anaphylactic reaction to either cephalosporin or PCN, there is no need to consider cross-sensitivity or to hold off on the use of the other drug. In case of anaphylactic reactions, skin testing is recommended before the drug use.
See below for a table of the shared R1-side chains as well as a flow chart for administration of cephalosporins in patients with reported penicillin hypersensitivity: