If watching someone else itch their skin makes you want to scratch away at your own, you're not alone.
Studies have shown that people are twice as likely to feel itchy when viewing footage of a person scratching their skin, than they are when they view footage of a person sitting still.
Medical experts have termed this domino effect as "the social itch".
In the above video, Dr Emily Grossman explains that while the standard itch may have evolved to alert us to insects on our skin, the evolutionary benefit of the social itch is less clear.
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She points out that primates also exhibit signs of social itching.
Considering this, there is reason to believe that we scratch when others do in order to prevent the spread of parasitic diseases from one individual to another in a close-knit community.
Scratching sensitises the skin of individuals in the group, enabling them to become more aware of potential parasites on their own skin.
Scientists have linked social itching to specific areas of the brain, known as mirror neurons.
"Mirror neurons are active when we perform an action, but also when we observe the same action being performed by another individual," Grossman says.
"It is possible that within the human brain, mirror neurons are involved in activating other areas of the brain to generate the social itch response."
So, if you want to test out the theory of social itching for yourself, stand up in your office and scratch your head.
(We do no take responsibility for any head lice rumours.)
