Severe cutaneous adverse reactions, including DRESS, SJS, and toxic epidermal necrolysis (TEN), involve pathogenic mechanisms in which cytotoxic CD8+ T lymphocytes, as well as certain pro-inflammatory eosinophil promoting cytokines (such as IL-4, IL-5, IL-9, IL-13), play a role [50,88,89]. Here, IL9 is linked to toxic epidermal necrolysis.