A thermal image of the human body is not a simple concept. The human body is a complex homeotherm, producing heat that must be lost into the environment. Human skin is the dynamic organ which serves as an interface between the body core and environment. Its temperature is therefore influenced by both internal and external conditions. Man is constantly changing his physical and physiological demands throughout his conscious hours. Local skin temperature is therefore influenced by air temperature, humidity, the presence of clothing, and a host of internal influences. Heat flow by conduction from underlying organs and blood convection in particular, warm the skin by the transfer of heat from the core. Changes in blood flow frequently occur, and contribute to the constant demand for thermal equilibrium.