Additionally, we found that inpatients that reported a PCN-class allergy were less likely to receive cefazolin and non-pseudomonal third generation cephalosporins, which can be safely used even in patients with severe IgE-mediated hypersensitivity reactions to PCN.17 Unsurprisingly, penicillins and first- and second-generation cephalosporins were less likely to be administered in “PCN-class allergy only” admissions. This evidence concerns the gene IGHE and Allergy.