IL17A and colitis: Accumulating evidence has revealed that AhR can mitigate colitis by decreasing the serum inflammatory cytokines/chemokines (e.g., TNF‐α, IFN‐γ, MCP‐1, and IL‐17) [47], enhancing the expression of IL‐10 and IL‐22 [12, 48], and strengthening the intestinal epithelial cell barrier [11, 14].