WE’VE ALL KNOWN forever that scratching isn’t the best way to handle an itch.
But now we know that not only does it cause scarring, it also makes the initial itch even worse.
There is a whole team at the Washington University School of Medicine in St Louis in the US that has dedicated itself to the problem.
They have discovered scientific proof that scratching an itch will make it worse.
Why?
Scratching can relieve itch by creating minor pain. But when the body responds to pain signals, that response actually can make itching worse.
Here’s the technical bit, which has been reported in the journal Neuron following the completion of a study on mice (although the same vicious cycle of itching and scratching is thought to occur in humans).
Scratching causes the brain to release serotonin, which intensifies the itch sensation.
So, why do we want to scratch an itch?
Scientists have known for decades that scratching creates a mild amount of pain in the skin, said senior investigator Zhou-Feng Chen, director of Washington University’s Center for the Study of Itch.
That pain can interfere with itching — at least temporarily — by getting nerve cells in the spinal cord to carry pain signals to the brain instead of itch signals.
The problem is that when the brain gets those pain signals, it responds by producing the neurotransmitter serotonin to help control that pain.But as serotonin spreads from the brain into the spinal cord, we found the chemical can ‘jump the tracks,’ moving from pain-sensing neurons to nerve cells that influence itch intensity.
Scientists uncovered serotonin’s role in controlling pain decades ago, but this is the first time the release of the chemical messenger from the brain has been linked to itch.
The study may be helpful for people with chronic itching issues as doctors are beginning to understand more about the pathways of itch and pain signals.
Scientists may now be able to interfere with the communication between serotonin and nerve cells in the spinal cord that transmit itch.
Those cells, known as GRPR neurons, relay itch signals from the skin to the brain. To work toward that goal, Chen’s team isolated the receptor used by serotonin to activate GRPR neurons.
To do this, Chen’s team injected mice with a substance that causes itching. They also gave the mice compounds that activated various serotonin receptors on nerve cells. Ultimately, they learned that the receptor known as 5HT1A was the key to activating the itch-specific GRPR neurons in the spinal cord.
To prove they had the correct receptor, Chen’s team also treated mice with a compound that blocked the 5HT1A receptor, and those mice scratched much less.
“We always have wondered why this vicious itch-pain cycle occurs,” Chen said. “Our findings suggest that the events happen in this order. First, you scratch, and that causes a sensation of pain. Then you make more serotonin to control the pain. But serotonin does more than only inhibit pain. Our new finding shows that it also makes itch worse by activating GRPR neurons through 5HT1A receptors.”
As Chen and co. continue to work on the project, they have one intermediary piece of advice.
Pay attention to mom’s advice and try not to scratch.”
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