A medical heating device is based on an electrical heater formed out of a self-limiting conductive material, such as a conductive polymer or ceramic. An electrical resistance that gradually changes with temperature characterizes the material such that heat production from electrical current through the material varies with temperature. A thermally insulating jacket contains the self-limiting heater element, which can be coupled to an electrical power supply. A probe thermally coupled to the heater extends outward from the jacket. The self-limiting medical heating device can be used by touching the end of the probe to target tissue, such as skin, adipose tissue, nerves, glands, vascular tissue, or abnormal growths or tumors to effect the desired treatment, typically by thermally ablating, cutting, or shrinking the target tissue where touched by the probe or in the vicinity therein.