One of the reasons for using heat packs is thermotherapy, which is theuse of heat for therapeutic purposes, especially for pain relief. In order for heat to provide the relief and help we need, and for it to be considered an effective remedy, it must be applied at a temperature higher than the physiological or natural temperature of our body, which is around 36-37ºC (96,8-98,6 °F). In order to benefit from thermotherapy, the product we use to apply heat to our body must be at least 40ºC (104 °F) or higher.