With the coronavirus pandemic, people have become a lot more aware of hygiene and keeping things clean. But what about the device that most of us handle many times a day, and even hold to our faces?
Well, first the good news: "The mobile phone is no germ spreader," says Markus Egert, professor of microbiology and hygiene at Furtwangen University in Germany.
Compared to the number of germs on human hands, the germ load on phones is negligible. "For healthy people in the household context, mobile phone germs pose no danger," Egert says.
"Modern smartphones in particular are super dry and smooth, which means that few germs can stick to them," he adds.
On the surface of a smartphone, germs would find little to eat and therefore couldn't multiply. In contrast, the bacterial load on old phone buttons was much higher.
How you use your phone will also affect how many germs it carries.
A reflection of the user
"The surface of the smartphone is a reflection of its user," says Sebastian Kloess from German IT industry association Bitkom. Those who rarely wash their hands, use their smartphones while eating and bring it into the bathroom transmit significantly more germs to their device than those who don't.
The state of the smartphone also has an impact on the germ load it can carry. "Bacteria, viruses and mould can stick particularly well to scratches," Kloess says.
Smartphone manufacturers such as Apple and Samsung offer cleaning tips on their websites. They advise switching off the device and unplugging all cables and accessories before cleaning.
The best way to clean the device is with a soft, lint-free, slightly damp microfibre cloth, the manufacturers advise. In the case of heavy dirt, a little soapy water can be used.
Even though many smartphones are waterproof, it's important that no moisture gets into any of the phone's connection ports. If it does, you should wipe it off immediately with a cloth.
There's no need to disinfect a phone that's in normal use, as there's no particular risk of infection, Egert says. The coronavirus can also be combated with soapy water, so disinfectant is not required and could also potentially damage the phone.
Other cleaning agents, such as glass cleaners and alcohol-based cleaners, can damage the grease-repellent coating on a smartphone's display, Kloess warns.
A smartphone's connection ports are particularly sensitive and should be cleanly carefully and without any moisture. Kloess recommends cotton swabs or a soft toothbrush. You can also use one of the small, hand-operated air blowers used for cleaning cameras, but compressed air cleaners should never be used, he says.
How often you should clean your smartphone ultimately depends on how you use it, says Bernd Glassl from Germany's personal care and detergents industry association. If you travel a lot, meet many different people or use your phone in the kitchen, you should clean it more often.