Summary What is known and Objective Hypersensitivity adverse drug reactions (HADRs) are associated with considerable morbidity and mortality. The aim of this study was to identify cases of HADRs within a hospital electronic health records (EHR) database. Methods Data were extracted from EHR through the Portuguese catalogue of allergies and other adverse reactions (CPARA). This registry allows the collection and sharing of information on HADRs in a structured and harmonized way across the healthcare system. This module is used by healthcare professionals to record HADRs within the EHR of each patient. It applies to patients admitted to hospital because of HADRs and also to inpatients developing such reactions during hospitalization. Data recorded from 2013 to 2017 within the Centro Hospitalar de Entre o Douro e Vouga (CHEDV) hospital (397 beds; ≈20 300 inpatients/year) were considered. The MedDRA® classification was used to codify HADRs. The ATC classification system was used to codify drugs. The concept of individual case safety report (ICSR) was considered for performing analyses. Results and discussion The database contained 464 valid cases (severe, n = 330; 71.1%), corresponding to 380 patients and 559 HADRs. Most patients were female (n = 254; 66.8%); the median age was 55 years. Approximately 0.1% local inhabitants and ≈0.4% inpatients have experienced HADRs over the study period. Most cases (n = 245; 52.8%) were associated with systemic antibacterials. Most HADRs were skin and subcutaneous tissue disorders (n = 266; 47.6%) and immune system disorders (n = 231; 41.3%). The pattern of suspected drugs implicated in anaphylactic reactions was the same as those involved in other HADRs. What is new and conclusion This registry contains HADRs that are relevant for the pharmacovigilance system, but none was spontaneously reported. The responsible authorities should address this problem. The results also reinforce the association between systemic antibacterials and HADRs.