Reciprocal contribution of Th17 and regulatory T cells in severe drug allergy

•Infiltrating and drug-specific CD4+ T lymphocytes from skin lesions in Stevens–Johnson syndrome/toxic epidermal necrolysis and drug-induced hypersensitivity syndrome were immunologically investigated.•Th17 and Treg cells in skin lesions dominated in between Stevens–Johnson syndrome/toxic epidermal necrolysis and drug-induced hypersensitivity syndrome, respectively.•Our finding suggests that Th17/Treg axis plays important roles of unique clinical manifestations in severe drug allergy.