Bathing in hot water has been a remedy for relieving pain since ancient times. The method has somewhat evolved from using a warm bottle of water or cloth to using a microwaveable heating pads. Nevertheless it has been the go to method for calming stomach pain, indigestion, menstrual pain or other pain in the abdomen. However this remedy was almost abandoned because of its archaic basis, but now British scientists have discovered, thanks to painstaking research, that hot water works in a very similar way to a painkiller.

To better understand this principle, we spoke to Dr. Maurizio Tommasini, Senior Consultant at the Unit of General Medicine and Hepatology of Humanitas.


How does the pain-relieving action of heat work?

“The action exerted by heat is that of vaso-dilatation. The heat generates a rush of blood in the desired location that results to a reduction of organ contractions i.e in an analgesic way. The mechanism of action has long been known in practice and heat does relax the muscles.

The University College London research, under the guidance of researcher Dr. Brian King, presented at the annual meeting of the Physiological Society also examined if a hot water bottle, acting on certain molecules could work similarly to painkillers. With the use of new techniques, the British demonstrated that heat (min. 40°C) acts at the level of molecules (just like a drug) by disabling the pain messages sent by the body to the brain. In practice, the proteins of the receptor of heat in a cell, block the pain receptor. This is just one more demonstration if the already known efficacy of heat against pain”.


Can heat replace a drug?

“It seems as an exaggeration to say that hot water can replace pain medications, even the most bland. It is certain however that it can help at enhancing the effect of analgesics and antispasmodics. Be careful though, not to overdo it… The risk of a burn is serious. Always place a cloth (eg. a t-shirt or a towel) between your skin and the source of heat”.


Can heat ease all types of pain?

“Absolutely not. Pain has different origins and is a complex mechanism that affects the peripheral nervous system, which activates the central nervous system. If for example, pain is caused by trauma then heat can be harmful. In these cases, you should use ice to try to block the formation of a hematoma. Another example is that of headaches where heat causes the pain to increase. Heat however, is useful in relieving pain caused by contractions These include back pain or cramps, in which the muscle needs to relax. It also helps menstrual pain, abdominal pain and renal colic.

The basic principle of this mechanism is the contrast between the temperatures. In practice, if the temperature in your body or locally is rising, such as in cases of hematoma, it would be useful to cool that part down with ice. If, however, there is no heat, then we recommend a treatment with heat. It is precisely the contrast between the two temperatures that acts as a painkiller”.


Are heating pads useful for colic diseases in children?

“Heat should not be used for infant colic because these are gaseous colic types. This means that approaching them with heat will cause the gas to expand and the colic worsens considerably. Furthermore, I would like to emphasize that it is preferable to avoid using a hot water bottle to relieve children’s pain. Their bodies are significantly smaller and it not only warms the affected area, but also the entire organism”.