Itching is socially contagious, says study

Ever wondered why you itch when another person scratches in front of you? A new study shows that scratching, just like yawning, is socially contagious and not a psychological response.

According to researchers, itching is highly contagious. Sometimes even its mention could make someone scratch. "Many people thought it was all in the mind, but our experiments show it is a hardwired behaviour and is not a form of empathy," said lead investigator Zhou-Feng Chen, director at the Washington University School of Medicine in St. Louis, US.

In the study, conducted on mice, the researchers found a chemical in the brain that makes them want to scratch when seeing someone else do it.
Further, the findings, published in the journal Science showed that the behaviour is hardwired in the brains, rather than a form of empathy with the original scratcher.

The chemical, GRP (gastrin-releasing peptide) -- a key transmitter of itch signals between the skin and the spinal cord -- caused mice to scratch when they saw others doing it. When it was blocked, they stopped.

"The mouse doesn't see another mouse scratching and then think it might need to scratch, too. Instead, its brain begins sending out itch signals using GRP as a messenger," Chen said.

"It's an innate behaviour and an instinct. We've been able to show that a single chemical and a single receptor are all that's necessary to mediate this particular behaviour," Chen added.

However, when the GRP receptor were blocked in the mice's brains, they did not scratch when they saw others scratch. The results may open new ways of treating people who suffer from chronic itching and skin diseases by developing a drug that blocks GRP, the researchers noted.