Fever is a common response of the body to infection and injury, tightly regulated by the balance between endogenous mediators known as cytokines that act either as pro-inflammatory/pyrogenic (interleukin (IL)-1β; IL-6, tumor necrosis factor α (TNFα)) or anti-inflammatory/cryogenic intermediaries (e.g. IL-10 and the IL-1 receptor antagonist (IL-1ra) [1]–[6]. The gene discussed is IL10; the disease is Fever.