- Eyelashes have evolved to be one third the width of the eye in length
- At this length, they reduce air flow to the eye, protecting from dirt
- Wearing fakes mean more air and dust hits the eyes, and they can dry out
By Madlen Davies for MailOnline
Published: 00:09 GMT, 25 February 2015 | Updated: 09:05 GMT, 25 February 2015
For the likes of Kim Kardashian, they are an essential part of the grooming regime.
But fake eyelashes may be doing more harm than good - and may in fact cause damage, researchers have waned.
A study found eyelashes have evolved to be one third of the width of the eye in length, so that they protect the eyes from dust and moisture evaporation, without blocking vision.
Experts found wearing longer lashes, increases airflow around the eye and leads to more dust hitting the surface.
This means the eyes are left unprotected - and are more likely to dry out.
Kim Kardashian's $13 false eyelashes soared after she wore them for her marriage to Kanye West, but experts have warned the beauty adornments can damage eyes
'This is why long, elegant, fake eyelashes aren't ideal,' said Guillermo Amador, a PhD candidate at Georgia Institute of Technology, Atlanta, US, the study's author.
'They may look good, but they're not the best thing for the health of your eyes.'
As part of the study the researchers measured 22 mammal species, from hedgehogs to giraffes.
They found the length of the lashes was always the same proportion: roughly one third of the width of the eye in length.
Experiments suggest the reason is evolution, because this is the best way to reduce the amount of evaporation and the number of particles getting into the eye, while giving the best field of vision.
To ascertain the best length eyelashes should be for healthy eyes, researchers attached synthetic lashes to an artificial eye and put them into a wind tunnel.
HOW EYELASHES PROTECT THE EYES - AND WHY FAKES DAMAGE THEM
Eyelashes have evolved to be a specific length, researchers found.
They should be one third of the width of the eye in length.
At this length, they reduce air flow to the eye, creating a layer of slow-moving air above the lens.
The majority of air essentially hit the eyelashes and rolled away from the eye, keeping the eye moist for longer and protecting it against particles.
Longer eyelashes increases airflow around the eye and leads to more dust hitting the surface.
This means the eyes are left unprotected and are more likely to dry out.
They monitored the water loss and looked at how many particles accumulated in the eye during a breeze.
When the lashes were the right length, a third the width of the model, they reduced evaporation and particle deposition by 50 per cent, as they trapped a protective layer of air on top of the eye.
They also stopped the eye from drying out and prevented dirt accumulating by creating a zone of still, or stagnant air just in front of the eye.
Longer lashes had the opposite effect, channelling airflow directly onto the eye surface, meaning it was hit by more particles and also tended to dry out more.
Professor David Hu, of the Georgia Institute of Technology, Atlanta, said: 'Our study demonstrates that eyelashes divert airflows, acting as a passive dust controlling system for the eyes.
'They reduce evaporation and particle deposition up to 50 per cent, indicating the evolution of eyelashes may have played a role in reducing the frequency of blinks, which replenish and clean the film of tears in the eye.
'Our experiments show that eyelashes of an intermediate length accrue the greatest benefits.'
The research is published in the Journal of the Royal Society Interface.
Cleopatra and other Egyptian noble women accentuated their eyelashes by painting them black using an ancient type of kohl.
The make up technique was also necessary for protection against the harsh desert sun.
Lashes were made mainstream in 1919 when Max Factor enhanced actress Phyllis Haver's by sewing real hair onto her own.
Celebrities such as Nicole Scherzinger (left) and RIta Ora (right) are pictured wearing false lashes, which experts say allow more dust and air to hit the eyes, drying them out
He is still credited with creating the first false lashes, although director D.W. Griffith had requested them for actress Seena Owen on the set of his 1916 movie Intolerance.
In the sixties, supermodel Twiggy's painted on lower lashes and full top set, often three pairs on top of each other, sparked a major trend which became her iconic look.
In 2009, Madonna wore a mink and diamond pair which cost $10,000.
And last year sales of Kim Kardashian's $13 false eyelashes soared after she wore them for her marriage to Kanye West.
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