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pruriceptors
Itch-sensing nerve endings caused by certain mediators; such as, stimulating agents including chemicals for immune response (such as, histamines) and pain relief (such as, opiods).

Scratching and rubbing interfere with the sensations arising from pruriceptors by stimulating various pain and touch receptors in the same areas.

Like many sensory systems in the body, activation of one signal, in this case that of the pain and touch receptors, causes "surround inhibition" of another signal, that coming from the pruriceptor.

The lack of pruriceptor firing "turns off" the itch sensation for a short period. Although it is helpful in relieving an itch, scratching offers only temporary relief and may cause the skin to become further irritated and possibly even to tear it, causing bleeding.

—Excerpts from
"How do itches come about, and why does it feel good to scratch them?"
answered by Mark A.W. Andrews, associate professor of physiology
at the Lake Erie College of Osteopathic Medicine;
Scientific American, June, 2007; page 80.
This entry is located in the following unit: pruri-, prur-, prurit- + (page 1)