It has been reported that obesity may be an aggravating factor for psoriasis. However, its pathological mechanism remains elusive. The adipocyte-derived hormone leptin primarily controls energy homeostasis by regulating appetite and modulates immunity. Strikingly, serum leptin levels are elevated in obese patients and positively correlate with body mass index. Additionally, leptin levels also correlate with severity of psoriasis, and knocking out leptin suppresses imiquimod-induced psoriatic inflammation in mice.