"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," said Brian King, a senior lecturer in physiology at University College London, who led the research.
Dr King found that if heat of more than 40ºC (104ºF) is applied to the skin near where internal pain is felt, it switches on heat receptors at the site of injury. These in turn block the body's ability to detect pain. He will present his findings today at the annual meeting of the Physiological Society.
[Guardian, 05 July 2006]
I once consulted my best friend who's an expert in fixing cars about a clangorous noise I heard whenever I drove my old car. He test drove my car and said, "That's nothing. 'Better get a good car stereo with great speakers."
"Huh? How will that solve my car's problem?" I scratched my head as I asked him.
"Easy...whenever you hear the noise, just turn on your car stereo to a high volume. You'll never hear the noise again," was his reply.
Very funny. Of course, he was kidding. But I was reminded of his reply when I came across the article above which said that scientists now know the physiology and mechanism how heat applied to an injury helps relieve pain. And they aren't kidding like my best friend was.
When someone feels pain in the gut, a separate mechanism is firing. Receptors called P2X3 have detected ATP, a chemical that pours out of cells when they are damaged. The heat response appears to shut these receptors down.
"You've got the heat receptor on one side and the ATP receptor on the other side that will recognise the pain. Both are present in our cells and yet, when you activate one, it switches off the other," said Dr King.
Just like what my best friend amusingly recommended for my noisy car. The same principle operates. You've got pain, apply a hot compress. Your body turns off the pain, and instead, what you now feel is the heat. It's a clear case of diverting your attention to a new sensation. It is a temporary relief at best, but with extreme pain, you and I know that is better than doing nothing at all.