Between Penicillins

Cross-reactivity between penicillins is possible due to a similar core structure and/or major/minor antigenic determinants.

The following share common major allergic determinants based on similarities in their core structure and/or side chains, and should be considered cross-reactive.
Amoxicillin
Ampicillin
Penicillin
Cloxacillin
Piperacillin
Ticarcillin