Drug reaction with eosinophilia and systemic symptoms (DRESS) and drug-induced liver injury (DILI) can hamper therapeutic strategy, contribute to multiple drug resistance and serious public health burden. Diagnosis (including allergy assessment) and management of these two severe hypersensitivity reactions in clinical practice are somewhat difficult and published scientific evidence is rather weak and limited. The first step is always represented by stopping all anti-tuberculosis (TB) drugs, treating reaction with systemic corticosteroids, and identifying the offending drug, even if it is often complicated by the patient's simultaneous intake of antibiotics. Patch tests and in vitro tests, such as lymphocyte transformation test, could bridge this diagnostic gap, but the available data are scarce and their sensitivity low. The re-challenge test is often necessary but places patients at risk for serious adverse reactions. The desensitization protocols are quite varied and not universally accepted. In this narrative review, we provide an update to the literature data on the management of DRESS and DILI with particular attention to the allergological work-up in the last decade.