THE old wives' tale that heat relieves stomach pain has now been scientifically proven.
Researchers found that heat, such as that from a hot-water bottle, did not just provide comfort and have a placebo effect.
They discovered it was capable of "deactivating" the pain at a molecular level, in a similar way to common painkillers.
The scientists hope the findings could help to lead to new drugs to alleviate internal pain.
The research, led by Dr Brian King of University College London, found that heat provided relief from internal pains, such as cystitis and period cramps, for up to an hour.
"The pain of colic, cystitis and period pain is caused by a temporary reduction in blood flow to, or over-distension of hollow organs such as the bowel or uterus, causing local tissue damage and activating pain receptors," Dr King said.
"The heat doesn't just provide comfort and have a placebo effect; it actually deactivates the pain at a molecular level in much the same way as pharmaceutical painkillers work."
The study used genetic engineering to make both heat and pain receptor proteins in the same human cell, which was then examined for interaction.
The team found receptors react once heat over 40C is applied to the skin near where the internal pain is occurring.
The heat receptors in turn block the effect of chemical messengers that cause pain to be detected by the body.
"The problem with heat is that it can only provide temporary relief," Dr King said.
He said future research would focus on discovering and developing drugs that blocked the pain receptors.