Seeing someone scratch makes you feel itchy too
If you feel itchy when you see someone scratch an itch, you're not suffering from any disorder.
A study, published in the British Journal of Dermatology, has suggested that seeing someone scratch an itch could make you feel itchy too.
Researchers at Liverpool John Moores University and the University of Manchester looked at whether images such as those of others scratching or ants crawling on skin, made people scratch.
They asked 30 people how they felt looking at these and "non-itch" images - and found visual cues did provoke a "scratch response".
And, in particular, it was watching another person scratching - rather than seeing the cause of an itch - that made people feel itchy themselves.
Experts said the work could help understand skin disorders.
"The results suggest that, whereas the sensation of itch may be effectively transmitted by viewing others experiencing itch-related stimuli on the body, the desire to scratch is more effectively provoked by viewing others scratching," the BBC quoted Prof Francis McGlone, a cognitive neuroscientist at Liverpool John Moores University, who led the study, as saying.
"Our findings may help to improve the efficiency of treatment programmes for people suffering from chronic itch," he added.
Another study, recently published in Proceedings of the National Academy of Sciences, used brain scans to show the same parts of the brain are activated when watching someone else scratch an itch as when someone does it themselves.
That team, including experts from Hull University, suggested that the activation of these areas could explain itching disorders where there is no physical cause.
"It was particularly interesting to see that contagious itch is not only elicited by observing someone scratching," said lead researcher Dr Henning Holle, of Hull University.
"Simply seeing potentially itchy stimuli, for instance ants crawling on the ground, seems to be enough to induce feelings of itchiness in one's own body.
"This suggests that a process of motor mimicking alone cannot explain contagious itch," Dr Holle added.