Skin melanin is associated with body temperature regulation in humans and mice.

Body temperature, a universally measured clinical indicator of physiological equilibrium, guides critical treatment decisions. Multiple studies have observed significant body temperature differences among racial subgroups, with Black patients consistently having higher temperatures than White patients. However, race is a social construct and not a biological category; thus, race alone cannot explain this temperature variability. We hypothesized that skin melanin, which often varies across racial categories, could explain body temperature differences. Here, using a prospectively enrolled human cohort study and a parallel mouse model, we demonstrate that skin melanin is associated with body temperature in humans and mice. In humans, colorimeter-measured melanin index was positively correlated with temperature. Likewise, we found that pigmented mice had higher temperatures than albino mice. Our results reveal that melanin could explain the consistent differences in body temperature observed across socially defined racial groups and suggest a potential role for melanin in thermoregulation.