The doctors of ancient Greece and China had it right when they applied cool and minty salves to soothe aches and pains, a new study suggests.
A synthetic treatment with the same properties as mint oil proves to be an effective painkiller when applied directly to the skin.
The new cooling compounds could be especially beneficial to millions suffering with the chronic pain of arthritis and diseases affecting nerve endings, scientists say.
"They work particularly well in ongoing pain states where the nervous system becomes hypersensitive, so even the lightest touch becomes painful," said study leader Susan Fleetwood-Walker, a professor of neuroscience at the University of Edinburgh in Scotland.
Healers in ancient Chinese societies treated injuries with mint oil, which contains anti-inflammatory properties and produces a cooling effect on the skin.
Cold compresses were also recommended in the fifth century BC by Hippocrates, who is considered the father of modern medicine.
Swelling and joint pain could be eased by the numbing effect of copious amounts of cold water, the ancient Greek scholar said.
The new compounds use the same soothing chemicals found in mint oil, but incorporate a few other important elements that work specifically with a pain receptor nerve in the skin called TRTM8, newly discovered by Fleetwood-Walker and her team.
"Chemicals in mint oil and cooling the skin can activate these painkilling nerves, but neither traditional method is very specific," she told LiveScience. "We have shown that the TRTM8 receptor is the critical molecular target for this painkilling effect."
Special analgesic ingredients in the compounds -- telling the receptor to turn off pain messages going to the brain—make them even more effective, the results showed.
Fewer side effects
The minty formula offers significant advantages over some other pain medications, which do not always work on sufferers of long-term pain, say the researchers.
"Some types of chronic pain, especially following nerve injury, are resistant to morphine," Fleetwood-Walker said. "These compounds act powerfully as pain killers on many types of chronic pain, including nerve-injury pain."
Because the compounds are applied externally, they should also come with a shorter list of potential adverse reactions.
"They seem to be just as powerful as morphine, but work through an entirely separate mechanism," she said, "with what we think will be less side effects."
The findings appear in an August issue of the journal Current Biology.
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