Penicillins
The reported history of penicillin allergy ranges from 0.7% to 10%.
There are four classes of betalactam antibiotics: penicillins, cephalosporins, carbapenems, and monobactams.
The first three all have bicyclic nuclei in contrast to monobactams (aztreonam), which lacks a second ring adjacent to the betalactam nucleus.