IL17A and psoriasis: Upon intravenous administration in psoriasis mice, nor@MSC‐EVs outperformed MSC‐EVs, nor‐NOHA, and the clinical biological agent anti‐IL17A in decreasing polyamines, inhibiting DC maturation via reducing self‐antigen generation, Th1/17 cells activation, and keratinocyte inflammation, thereby modulating both local and systemic metabolic and immunological disorders.