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BackgroundHypersensitivity to beta-lactam antibiotics are usually defined only by the history of suspected previous reaction to these medicines. This definition, however, can erroneously restrict the use of these important therapeutic resources if not assessed by the proper tests. The objective was to assess the presence of hypersensitivity to beta-lactams through adequate testing.MethodsThirty-three patients were referred to our allergic clinic for testing of penicillin hypersensitivity in the period from 2008 to 2011: 22 (66.6%) females and 11 (33.4%) males, with ages ranging from 8 to 88 years. The first 24 (72.7%) patients were tested using only penicillin G, in the form of a prick test followed by an intradermal test with immediate reading, according to the Brazil Ministry of Health protocol (group I). The remaining 9 (27.3%) patients (group II) were subjected to the adaptations of standards-based assessment of hypersensitivity reactions to beta-lactam antibiotics, according to the algorithmic recommendations of the European Network Drug Allergy (ENDA), which includes a prick test and intradermal test with penicillin G, amoxicillin and the suspected beta-lactam, such as clavulanic acid or cephalosporins, with immediate and delayed readings. Patients who had negative skin tests results underwent a provocation test, which is considered the gold standard in determining drug hypersensitivity. In-vitro tests available in Brazil (specific IgE to penicillin and amoxicillin) were performed in patients with a history more suggestive of adverse reactions. It was respected the ENDA recommendation of not subjecting patients with severe reactions to this protocol.ResultsOf the 33 patients, 28 (84.8%) had negative results for the tests. One patient in group I showed inconclusive results. Four patients (12.2%) in group II had positive tests, including 3 for penicillin G and one for amoxicillin.ConclusionsThe results demonstrated that the clinical history collected by medical questionnaires is not the determining factor in confirming a patients’ reaction to penicillin, and shouldn't be the only parameter used to exclude potential future prescriptions. In addition, the results denote that hypersensitivity to other beta-lactam antibiotics should be evaluated in a more proper way for a fuller understanding of each case.