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.
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.)
10 Foods For Healthy Skin
Flaxseed Oil/Borage Oil(01 of10)
Open Image ModalHigh in essential fatty acids, both Omega 3 and 6, these seed oils were found in a French study to reduce redness when skin was purposely irritated. "Both [borage and flaxseed] groups showed significant decreases in skin roughness and scaling after 12 weeks, while no change was observed in the placebo group." (credit:Shutterstock)
Green Tea(02 of10)
Open Image ModalBrewed green tea is incredibly high in antioxidants, important for eliminating free radicals which can damage skin cells and cause signs associated with aging. Polyphenols in green tea have been found to rejuvenate dying skin cells. Green tea also has vitamin C, a potent antioxidant which reduces inflammation and protects cell membranes.
Fatty Fish(03 of10)
Open Image ModalFish like salmon, herring, mackerel, whitefish and char are high in Omega 3 fats. Fatty fish are particularly high in EPA and DHA, two forms of the essential omega 3s that are associated with decreased inflammation which can be the root cause of skin problems. They also help to maintain the healthy structure of cell walls allowing for the right nutrients to get in while the waste products are kicked out. Healthy cell membranes equals healthy skin. (credit:Shutterstock)
Berries (04 of10)
Open Image ModalBerries are considered some of the most potent sources for antioxidants which protect skin cells from free radical damage. When protected from damage at the cellular level the skin looks younger for longer. Strawberries are also a good source of silica, a vital trace mineral for healthy skin and connective tissue. (credit:Shutterstock)
Celery (05 of10)
Open Image ModalA great source of silica, a trace mineral that strengthens the body's connective tissues and is vital for healthy skin. Other sources of silica include leeks, green beans, garbanzo beans, strawberries, cucumber, mango, celery, asparagus and rhubarb. (credit:Shutterstock)
Cucumbers(06 of10)
Open Image ModalCucumbers contain vitamin C and caffeic acid, two antioxidants that help fend off wrinkles and sun damage. Vitamin C boosts collagen and elastin, which helps keep skin looking vibrant. Caffeic acid protects skin cells from UV radiation. Cucumbers' natural anti-inflammatory properties calm and soothe skin reddened by rosacea or sunburn when applied topically. Cucumbers also contain silica. (credit:Shutterstock)
Carrots (07 of10)
Open Image ModalCarrots contain both betacarotene (precursor to vitamin A) and vitamin C. Vitamin A is necessary for the growth and maintenance of healthy skin cells. Dry skin or red bumps on the skin are possible symptoms of vitamin A deficiency. Betacarotene acts as an antioxidant to neutralize harmful free radicals, helping to prevent wrinkles, resist infection and keep skin youthful. (credit:Shutterstock)
Pumpkin Seeds (08 of10)
Open Image ModalDon't throw out the seeds from that jack-o-lantern. Pumpkin seeds contain zinc, an important mineral component of healthy skin. Zinc is especially important for acne sufferers, (acne may actually be a symptom of zinc deficiency). Zinc helps to control the production of sebum in the skin, and may also act by regulating some of the hormones that create acne. (credit:Shutterstock)
Methyl Sulfonyl Methane (09 of10)
Open Image ModalIf you're looking to really see some changes in your skin, try supplementing with methyl sulfonyl methane (MSM), a particularly bio-available form of sulphur. Although it's available in some wild-grown fruits and vegetables that have had exposure to rain water, MSM is chemically altered and destroyed when foods are processed, heated, or dehydrated, so the best source is from supplements. Sulfur produces flexible skin and muscle tissue, helps prevent wrinkling, hydrates collagen and increases the growth of hair and nails. There's a reason hot sulfur baths are valued in spa circles! (credit:Shutterstock)
Water(10 of10)
Open Image ModalRemaining properly hydrated is one of the best things you can do for your skin. Caffeinated beverages, sugar drinks and juice don't count - it has to be water! Water hydrates skin cells, allowing them to move cell wastes out and move nutrients in more easily. A properly hydrated body sweats more efficiently, keeping skin clean and open. (credit:Shutterstock)