Sometimes, itching like yawning, can be contagious researchers have found.
Contagious itch is visually transmitted, said Dermatologist Gil Yosipovitch of Wake Forest Baptist Medical Center, and anecdotal evidence suggests it occurs in daily life when we see other people itch and scratch.
A team, led by Yosipovitch, set out to systematically investigate contagious itch and to get an insight into what's happening in the brain during this transmission.
Yosipovitch and co-researcher Alexandru Papoiu, examined the effect of visual cues of itch on the perception of a local itch inducted experimentally and in the induction of scratching, in a controlled setting.
The scientists compared 14 healthy subjects, who received histamine or a saline control applied to their forearm, with 11 patients who had atopic dermatitis (AD). All study participants were monitored as they watched short video clips of people scratching or in a relaxed state, and their behavior analyzed.
Researchers found those with AD had higher itch intensity and scratched more frequently while watching the videos of other subjects scratching. Of interest, said Yosipovitch, is that the visually induced itch had a scattered, wide body distribution of scratching.
"This shows that the power of the brain is pretty extreme," said Papoiu. "This speaks to a core of our being, to being particularly vulnerable to suggestions of itch, which can easily trigger a response from our central nervous system."
The new findings appear online in The British Journal of Dermatology.