Our brains are full of weird mysteries. Chief among these is without a doubt the mystery of why itching seems to be contagious. Why does seeing someone scratch, or even having itching mentioned, send some people into a scratching frenzy.
Well, it's possible that this isn't just some random coincidence or a figment of the imagination. It really happens, and scientists might know why (feel free to pause and scratch that itch).
Itching may actually be contagious. SciShow, in a video about the broader subject of itching, notes that one set of researchers on the subject gave a lecture to an unsuspecting crowd on the topic of itching. While that seems like a needlessly cruel mind game, both verbal and visual stimulus about itches got the audience scratching. Furthermore, it has not only been shown to be a reality for people, other researchers have proven the phenomenon with monkeys.
And those aren't the only studies that have shown the phenomenon is real. A separate study at Wake Forest Baptist Medical Center, published in the British Journal of Dermatology in 2011,reported that similar triggers induced itching on their subjects, particularly, in this study, among subjects with skin conditions. This was also repeated in a study at the universities of Hull and Sussex in 2012.
To understand why contagious itching may be happening, it's important to understand some of the reasons we feel itchy in the first place. It's thought to be an evolutionary development that creates an impulse (the almighty scratch) to remove irritants like bugs, plants or other foreign objects that could do damage to the body.
So, if someone in your family or your herd is scratching, you might become itchy as an evolutionary reaction because there's the possibility they are scratching due to a parasite, bug, or other irritant in the immediate environment. That means it's possible you have come into contact with the irritant as well, and scratching an itch is a quick impulse to remove whatever bug Dave the Monkey brought back to the monkey tree.
There's a lot we don't fully understand about "socially contagious" activities like yawning and itching, but rest assured that you're not crazy when it happens to you. When someone else scratches, many of us start to itch in response.