Scientists have shown scratching helps relieve an itch as it blocks activity in some spinal cord nerve cells that transmit the sensation to the brain. However, the effect only seems to occur during itchiness itself - scratching at other times makes no difference.
While it is widely-known scratching relieves an itch, the physiological mechanisms for how this works are little understood. The University of Minnesota study appears in Nature Neuroscience. Previous research has suggested that a specific part of the spinal cord - the spinothalamic tract - plays a key role.
Nerve cells in this area have been shown to be more active when itchy substances are applied to the skin.
Blocks activity
The latest work, in primates, found that scratching the skin blocks activity of nerve cells in the spinothalamic tract during itchiness - preventing the spinal cord from transmitting signals from the scratched area of skin to the brain.
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