Cyto-LTT reveals dose-dependent T cell activation in delayed drug hypersensitivity reactions, challenging the notion that drug allergic reactions are dose-independent. The assay not only identifies the culprit drug but also quantifies immune activation strength. Stronger responses were more frequent in DReSS, suggesting the test may also inform risk assessment-particularly in guiding caution with structurally related compounds or in patients at risk for severe or recurrent reactions.