Itch
The sensation of itch, which shares many nervous pathways with pain, has long been a mystery. One reason is that it can be conjured up entirely by the brain. Just thinking about something tickly, or even watching someone else scratch, can ___ 31 ___ us off. Efforts to find out why this is, and why only scratching makes it stop, have led researchers to study how itch is processed in the skin, spinal cord and brain.
Itch, like chronic pain, is a surprisingly common problem. It comes as a side effect of opioid painkillers, the use of which has rocketed in recent years. It also comes with skin conditions, such as eczema, as well as nerve damage, kidney disease and allergies. An estimated one in five of us will experience chronic itch at some point, and current remedies are providing little ___ 32 ___ .
The most common treatments are antihistamines, which block the part of the immune reaction that causes itching when we are bitten by a bug, for example. Not all itches are immune-related, however, and antihistamines have proven to be ___ 33 ___ for most forms of chronic itch.
In recent years, researchers have discovered new kinds of receptors in the skin and spinal cord that play a role in the sensation of itch. They are working to figure out what naturally activates these receptors in the hope of ___ 34 ___ drugs that can deactivate them.
Further clues on how to tackle itch come from brain imaging studies. Many brain areas activated by pain are also active during itch, but one area that seems distinctively responsive to itch is the precuneus. This brain area is involved in visual processing and memory, says Gil Yosipovich at the University of Miami. "We can’t pinpoint what it does in itch, but it’s ___ 35 ___ activated with itch as opposed to pain," he says.
For now, though, the single most effective way to get rid of an itch is what we do instinctively: to scratch.
STEPHANI SUTHERLAND, NEW SCIENTIST