As with some kinds of pain, subtle reminders of an itching sensation can get people scratching, often without being entirely aware of it.
“I give lectures about itching,” Dr. Giesler said, “and I’ll stand up there in front of a whole roomful of people, show a few slides and pretty soon I’ll look out and 90 percent of the audience is scratching.”
Like yawning, itching also seems to be contagious, which suggests a significant top-down influence from the brain.
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