A review of the subject provides some analysis and guidance. Salient points include the epidemic of over diagnosis – most patients don’t remember why they had penicillin or what kind of reaction they had. Some studies have shown as little as 1% true allergy in patients labelled as penicillin allergic. Many receive Penicillin subsequent to an “allergic” reaction. Other studies have shown waning and disappearance of allergies over time. Cross-reactivity to cephalosporins in the population is probably near 1% and not 10% as once reported.
Using alternative antibiotics risks increasing resistance and C Difficile / VRE infections
While there are differences in structure of side chains, as a general guide they recommend proceeding with agents like Cefazolin where s previous reaction was mild and skin only. In major reactions or Stevens-Johnson syndrome it is advised to avoid all B-Lactams including penicillins, cephalosporins, monobactams and carbapenems.