Penicillin allergies are not always lifelong. Approximately 50% are lost over five years. A reaction to penicillin during a childhood infection is unlikely to be a true allergy. Only 1-2% of patients with a confirmed penicillin allergy have an allergy to cephalosporins. In patients with a low risk of severe allergic reactions, cephalosporins are a relatively safe treatment option. Patients with a history of delayed non-severe reactions, such as mild childhood rashes that occurred over 10 years ago, may be suitable for an oral rechallenge with low-dose penicillin. This should be done in a supervised hospital environment. In many cases, with appropriate assessment and allergy testing, it may be possible to remove the penicillin allergy label. stay, 3 hospital readmission rates, 10 surgical site infections, 14 and admissions to intensive care units. 15 Similarly in general practice, penicillin allergy labels are associated with an increased risk of death and MRSA infection or colonisation. 16 Impermanent allergy It has been demonstrated that more than 90% of patients labelled as having a penicillin allergy would be able to tolerate penicillins following appropriate assessment and allergy testing. 17-19 Even penicillin allergies confirmed by skin tests can wane over time. Half the patients who have a positive skin test for penicillins will lose that reactivity after five years. 13,20 There is therefore interest in penicillin allergy 'de-labelling'. This is the removal of the allergy label following either allergy history reconciliation or testing (oral provocation or skin testing). What is true penicillin allergy? The classification of a patient-reported penicillin allergy label is the first important step in appropriate care (Table 1). Before prescribing, ask patients about their allergies, as not all allergies may have been documented in their medical records. Conversely, some reactions labelled as allergic may be other types of adverse events. Ask about the clinical features of suspected reactions. Allergic cross-reactivity The beta-lactam antibiotics include penicillins, cephalosporins, carbapenems and monobactams.