Electric heating pads use electric heating coils, which not only emit high levels of electromagnetic radiation, but only heat your skin (or burn it, as has happened to so many people).
The Food and Drug Administration (FDA) and the Consumer Product Safety Commission (CPSC) have received many reports of injury and death from burns, electric shocks, and fires associated with the use of electric heating pads. These incidents have occurred in nursing homes, hospitals, and at home. In most cases, they could have been avoided by careful inspection and proper use of the heating pad.
Most of today's household heating pads are what has become known as "electrical pads" (as opposed to , or the now-antiquated ). In the case of an electrical pad, the power is provided via an outlet. Once turned on, the user chooses a heat setting (most blankets have somewhere between 5-10 settings). The electricity generates heat that is distributed by way of nichrome coils. There is at least one layer of plastic - and/or fabric - separating those coils from the skin. Electrical heating pads need to be strictly regulated to ensure they don't get much hotter than 85 degrees. Most pads also come with some type of auto-off function to prevent them from becoming fire hazards.