Tags: scratching | itching

Why Scratching Makes You Itch More

By    |   Thursday, 30 October 2014 03:39 PM

It is one of those medical-science questions that has long perplexed the experts: Why does scratching an itch make it worse?

Now, scientists from Washington University School of Medicine in St. Louis think they have the answer: New research involving mice suggests that scratching causes the brain to release serotonin, which intensifies the itch sensation, Medical Xpress reports.

The findings, reported online in the journal Neuron, indicate the same vicious cycle of itching and scratching that occurs in mice also takes place in humans. And the research provides new clues that may help break that cycle, particularly in people who experience chronic itching.
Scientists have long known that scratching creates minor pain in the skin, said lead researcher Zhou-Feng Chen, director of Washington University's Center for the Study of Itch. That pain can interfere with itching, 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," Chen explained. "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."
Serotonin is involved in growth, aging, bone metabolism and in regulating mood. Antidepressants like Prozac, Zoloft, and Paxil increase serotonin levels to control depression. Chen explained that the new research indicates it might be possible to interfere with the communication between serotonin and nerve cells in the spinal cord that specifically transmit itch.
"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 …."

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Scientists have determined why scratching makes an itch worse.
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Thursday, 30 October 2014 03:39 PM
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