Hot water bottle 2.0l + cover Scandinavian.Scientists at UCL (University College London), have found the molecular basis for the theory that heat from a hot water bottle on the skin soothes internal pain such as abdominal pain. The heat not only provides comfort, but also alleviates pain on a molecular level, as medication does. The scientists discovered that if you put heat above 40°C on the skin near the internal pain, the heat receptors are activated and the pain receptors are switched off. By switching off the pain receptors, the heat can ensure that the pain is no longer felt by the body.