Many studies have proven gene polymorphisms in cytokines such as IL‐1α (12–28), IL-1β (12, 16, 18, 24, 29–55), IL-2 (56–60), IL-4 (61–73), IL‐6 (74–86), IL-23 (87), IL-10 (16, 42, 84–86, 88–110), IL-13 (66, 111, 112), IL-17 (60, 73, 87, 113–117), TNF-α (16, 35, 38, 44, 48, 85, 118–132), IFN (70, 85, 102, 133–136), and TGF (42, 137–143), which often play various vital roles in periodontitis immune pathogenesis or in the prevention of periodontitis immune responses. The gene discussed is IL13; the disease is periodontitis.