IT HAPPENS TO ALL OF US — beginning, perhaps, as a little tickle, hardly noticeable.
Maybe you're in an important meeting and you don't want to fidget. Or maybe your hands are full. So you try to ignore it, but the sensation grows -- an irritating, niggling feeling that gradually occupies more and more of your attention.
Finally, you can't take it any longer.
You have to scratch the itch.
Itching is as fundamental a sensation as pain and hunger, one we share with other creatures: "Every two-legged and four-legged animal itches and scratches," says Dr. Gil Yosipovitch, a dermatologist at Wake Forest University Baptist Medical Center in Winston-Salem, N.C. Yet for such a seemingly simple sensation, it's also surprisingly complicated.
Scientists have long wondered why pain -- for example, from scratching -- relieves an itch. They've searched for the nerves that send the itchy signal to the brain, and they've wondered what switches those nerves on and off.
And doctors and patients alike have wondered why the sensation can be so hard to expunge in those unfortunates who experience the extreme end of itching -- an itch that just won't go away.
Today, a small group of dermatologists and neuroscientists are starting to look at the biological mechanisms that lie behind itching. As they do so, they are finding curious overlaps between itching and that different-seeming sensation, pain. Though sometimes pain is itching's opposite, the latest findings are showing more and more similarities between the two.
And as they begin to understand the sensation's biology, dermatologists -- including ones at the world's only clinic dedicated entirely to the treatment of itch -- are developing new therapies for people who suffer the torment of chronically itchy hides.
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An unbearable sensation
For most people, itching is only a mild annoyance, relieved by a quick scratch or maybe some skin cream. For others, the itch stays, stays -- and stays.
"It starts like any other itch, like you've been bitten or something," said David Hayes, a Los Angeles computer technician who has psoriasis, a noncontagious disease that causes skin inflammation, probably due to an overactive immune system. "But then it keeps on going. You've got to scratch it, and you've got to keep scratching until you're almost bleeding before it stops."
