Why itching really is contagious

IF YOU’VE ever seen someone scratching and suddenly felt the need to have a good itch yourself, then you’re not alone.

A study has found that itching really is contagious as our brains are wired to start scratching when we see others doing so.

American scientists found a brain circuit that can trigger ‘social itching’. However, they also found a chemical that can turn this circuit off.

They showed mice a video of a mouse scratching and found that it made the creatures follow suit. But when given a chemical called GRP – gastrin releasing peptide – the mice didn’t scratch when they saw others doing so.

The researchers said that in mice, at least, itching is a hardwired behaviour and not a form of empathy.

The findings, by the Washington University Centre for the Study of Itch, could lead to new ways of treating people who suffer from skin diseases by developing a drug using GRP.

Dr Zhou-Feng Chen, director of the centre, said the contagious itching behaviour the mice engaged in is something the animals can’t control. He said: ‘It is an innate behaviour and an instinct. We have been able to show a single chemical and a single receptor are all that’s necessary to mediate this behaviour.’

The discovery may help scientists understand the neural circuits that control other contagious behaviours such as yawning.

In the study, published in Science, the researchers put a mouse in an enclosure with a computer screen, then played a video that showed another scratching.

Dr Chen said: ‘Within a few seconds, the mouse in the enclosure would start scratching, too. This was very surprising because mice are known for their poor vision.’

Matthew Gass, of the British Association of Dermatologists, said: ‘Itch is often the worst symptom for people with skin disorders, and any research into its causes which may lead to new methods of alleviation will be greatly welcomed by the millions of skin patients.’