Further studies found that in biologics, relative to tumor necrosis factor-α inhibitors (TNF-αi), interleukin-17 inhibitors (IL-17i) and interleukin-23 inhibitors (IL-23i) are both protective factors in flare-up of psoriasis [IL-17i: OR (95% CI) = 0.412 (0.189–0.901); IL-23i: OR (95% CI) = 0.291 (0.097–0.876)]. Here, IL17A is linked to psoriasis.