We want to continue the discussion on drug-induced agranulocytosis and neutropenia1,2 and point to the differentiation between underlying allergic or cytotoxic mechanisms that may be important: preventing allergic reactions usually requires avoidance of the culprit drug for a lifetime. The in vitro lymphocyte transformation test has proven more sensitive than skin tests for the diagnosis of drug allergy, and is effective regardless of the clinical phenotype of the reaction because drug-sensitized lymphocytes are found in antibody- or cellular-mediated immune reactions.3