Sight of itching Scratching can be contagious

A British study by researchers from Hull University has found that scratching can be contagious to neurotic-susceptible people. If they see them, "that someone scratched the skin, they also have to scratch", so the resume of the scientists. It may now be possible to explain why some people suffer from persistent itching, although no skin diseases can be diagnosed.

13.11.2012

For some time scientists have known that scratching, like laughing or yawning, can be downright contagious. So far, the connections with the phenomenon "itchy skin rash" have not been clearly proven. After all, not every person has to scratch his or her skin immediately when the other person is itching. In the course of an experiment, scientists at Hull University found that not all but only certain people were significantly more susceptible. "Particularly emotionally unstable people even feel itchy when they watch a person scratching". According to researchers, even observing activates certain regions of the brain that are also activated during itching. It is possible that this is an excessive activation in the brain, a kind of "scratch matrix", responsible for the constant itching. The itching feel many people, although a dermatologist could find no organic cause, as the research team in the journal "PNAS" write.

Scratch films caused 60 percent to itch animate
During the study, the 33 male and female participants were shown video clips of people scratching or tapping on specific parts of the body. While watching, the subjects were filmed without their knowledge. After each video sequence, the participants should judge for themselves how much it itched. First, it was found that the subjects felt a greater itching scratching than watching the knocking. More than 60 percent were infected by scratching and itched at least one of the video itself. Especially if in the video, the left upper arm was scratched, led to the following itch, the researchers write in their study report.

Neuroticism made it more prone to itching
In the further course it turned out that obviously people develop a higher tendency to itching if they are more prone to neuroticism. Neuroticism (derived from neurosis) is a specific personality trait in which people are more susceptible to negative emotions of their environment or stress. Differences between women and men could not find the science team. The contagious effect was the same in women and men. "Surprisingly, the ability to empathy did not matter," said study director Hennig Holle. Subsequent tests showed that itchy individuals had no greater capacity for empathy or compassion than others less prone to scratching.

In the third step, the scientists had some study participants watch videos, while a computer tomograph (MRI) scanned the activities of the brain. Numerous areas of the "scratch matrix" were activated. In the case of the "neurotic participants", the regions were particularly strongly activated. The specific areas of the brain are especially stressed when simulations of activities are played through in the brain or chemicals on the skin irritate itching. This shows that "in organic and mental itching the same areas in the brain are claimed," said the team.

Activation of the scratch matrix trigger for mental itching
"We assume that the activation of the central scratch matrix can trigger psychogenic itching diseases," the researchers summarized in the "Proceedings of the National Academy of Sciences" (doi: 10.1073 / pnas.1216160109). "Subjects with a higher neuroticism value were significantly more likely to be infected by the itching". Thus, it can probably also be explained why some patients suffer from constant itching, although there are no organic skin diseases and the skin is not irritated. Accordingly, it could be that in those the "Juck matrix" is over-sensitive. Further research must now clarify which functions occupy individual areas of the brain and how the findings in the treatment of mental itching could be included. (Sb)

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