Kennard L, et al. - Researchers intended to clinically characterize, in detail, a cohort of patients referred with suspected flucloxacillin (a narrow spectrum, beta-lactamase resistant penicillin) hypersensitivity. This study included 108 patients presenting to 4 UK centers, for whom, data on demographics, presentation, investigation and management were retrospectively analyzed. Hypersensitivity to flucloxacillin was detected in 40/108 (37%) patients; immediate and non-immediate hypersensitivity was detected in 33/40 (82.5%) and 7/40 (17.5%), respectively. According to findings, more common were immediate hypersensitivity reactions to flucloxacillin as compared with delayed hypersensitivity reactions. In delayed reactions vs in immediate, higher cross sensitization to other penicillins was noted. The immediate vs non-immediate group had higher NPV of intradermal testing. The diagnostic gold standard was drug provocation testing.