Sep. 13, 2011 at 8:30 AM ET
WARNING: Reading the following post will make you itchy.
There probably aren’t any tiny ants feeling their way over your limbs and across the back of your neck right now. But wouldn’t you feel better scratching anyway?
Why is it that seeing, discussing, or even just thinking about creepy crawlers makes us feel itchy all over? It turns out the experts aren’t sure.
University of Pennsylvania neuroscientist Dr. Wenqin Luo places the blame for phantom itch on memories of an itchy past. Thinking about bugs, she explains, might prompt memories of previous experiences – “itchy associations.”
Why, then, doesn’t thinking about injuries prompt our bodies to feel phantom pains?
Dr. Luo offers the following theory: “Compared with itch, pain is a serious protective mechanism that triggers avoidance behavior. Thus, the threshold to trigger a pain sensation may be much higher than that of itch.”
Basically: If our brains registered pain (a danger) as easily as they do itch (an annoyance), our bodies would be sent into constant states of false alarm.
Dr. Glenn J. Giesler, Jr., a neuroscientist from the University of Minnesota offers a slightly different guess as to the phantom itch culprit: Maybe our skin always experiences the tiny sensations capable of causing light itch – but we only notice them when we’ve already got itch (or its creepy crawly causes) on the brain.
“It is amazing to me how easy it is to induce itch in others,” says Giesler. “Whenever I give a talk on the topic, I am amused at the percentage of people in the audience who start scratching.”
“Perhaps,” he guesses, “the threshold for sensation of itch is lowered by thinking about it.”
Dr. Gil Yosipovitch is a professor of dermatology at Wake Forest Baptist Medical Center in North Carolina. He’s also the founder of the International Forum for the Study of Itch.
He explains that a related phantom itching phenomenon, “contagious itch” (that is: itch felt not because of a physical stimulus, but because we see another person scratching), is a behavioral response similar to contagious yawning. Both are our bodies’ way of subconsciously expressing empathy and compassion for our fellow humans.
In fact, Yosipovitch says, sympathy scratching spans species – primates exhibit it too.
So, after all that, are we any closer to solving the mystery of the phantom itch?
Please. We’ve barely scratched the surface.