September 12, 2008
Why That Tender Touch Really Could Stroke the Pain Away ; Hopes Discovery Will Lead to Host of New Treatments
Scientists have discovered a distinct set of 'pleasure nerves' in the skin that can alleviate pain when they are gently stroked.
They believe that the discovery could lead to new treatments for conditions ranging from chronic itching to depression.
Tests on human volunteers have found that a painful stimulus applied to the skin can be eased significantly by gently stroking the pleasure nerves in a nearby part of the body, said Professor Francis McGlone of Unilever and Liverpool University.
The nerves are part of the so-called C fibres of the nervous system, which are known to be responsible for producing the sensation of pain in the skin. But instead of stimulating pain, a subset of the fibres also appear to stimulate pleasure.
"If you get a piece of grit in your eye, have a toothache, or bite your tongue, it hurts so much because there are more C fibres there. The research we have been doing is building evidence for another role of C fibres in the skin that are not pain receptors, but are pleasure receptors," Prof McGlone said.
"There is another sensory nerve fibre system in human skin that appears to code for the pleasant and affiliative aspects of touch we are all familiar with, such as when grooming or being cuddled."
There is growing evidence that touching the skin and gentle stroking of the body stimulates an evolutionary ancient part of the nervous system that makes people feel good when cuddled by a loved one or groomed by themselves.
"Grooming behaviours are not at a functional level for removing dirt. I think we groom primarily to feel good.
"Grooming is a rewarding behaviour that aids well-being. One of the hallmarks of clinical depression is that people stop looking after themselves, they stop grooming," he told the British Association for the Advancement of Science at Liverpool University.
Some parts of the body are richer in the pleasure nerves than others. They are not present at all, for instance, on the palms of the hands or the soles of the feet.
"We've tested everything from forehead, forearm, upper leg and the face and we find heterogeneity in response to touch.
"They haven't been found in the genitalia, but I think another system is responsible for tactile reward in that area," Prof McGlone said.
"With pain it has been clearly established that without such a sense we would not survive, and now we are beginning to understand that without a sense of pleasure, or reward, behaviours that we take for granted, like the caress between lovers and the nurturing of babies we would also not survive," he added.
Doctors have already realised that premature babies do better when cuddled straight after birth, and there may be many other medical conditions that could benefit from a better understanding of the pleasure nerves of the skin.
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