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, according to a story on MSNBC.com titled "Spiders! Ants! Did that make you itchy? Here's why”
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.