Touchscreen tablets and phones are popular in almost every respect but one – the smears that fingers leave on the screen.

Fingers produce oils and other substances that can smear screens

Every owner of a gadget piloted via a touchscreen has spent time rubbing it with a tissue, a cloth or a sleeve gripped round the heel of the hand to banish those unsightly marks.

It's not that human fingers are filthy. Those smears come about thanks to a mix of physiology and good grooming habits, said Steve Block, an electronics industry scientist at Dow Corning, which makes coatings that get applied to touchable screens.

"There's a whole range of things that can contaminate those surfaces," he said. "There are natural oils on the fingers as well as the lotions people put their hands. Then there's cosmetics and the times when you hold your telephone up to your ear and it's sweaty."

Small wonder then that the sight of those smears is unsettling.

Viral load

Thankfully, there is no reason to fret, as those smears are safe if your touchscreen gadget is kept just for you, said Prof Charles Gerba, a microbiologist at the University of Arizona.

"Touchscreens are a source of a wide range of microbes, but not much of an issue if you do not share it among other people – since, if you are the only one using it, it's only your germs," he told the BBC.

Sadly, that is not the case when those touchscreens are put to more promiscuous use, such as in a supermarket at the self-checkout, by patients in a doctor's waiting room or in a family that passes the gadget around.

More of the story, click image