Take a look at your mobile device. Do you see oily fingerprints on the touch screen? Dust and crumbs forming particulate frost in the corners? Is that really a hair stuck at the screen’s edge?

Because our electronics are constantly within our grubby grasp, they can get pretty gross. They get taken into public restrooms, passed around to share photos, handed off to runny-nosed toddlers and pressed against our sweaty skin in the gym.

What accumulates is a germy stew worse than what’s on the bottom of your shoe.

“That devices can be a source of disease transmission is not a subject of debate anymore,” said Dr. Dubert Guerrero, an infectious disease specialist at Sanford Health in Fargo, N.D.

So it’s a good idea to keep your devices clean, not only to keep from getting sick but also to maintain resale value when it’s time to upgrade. But cleaning an electronic device is tricky, because you don’t want to damage it. Worse, manufacturers don’t give you much guidance. Still, you can do it — if you’re careful and conscientious.

Microfiber first

Guerrero and his colleagues found that regularly wiping down your device with a moist microfiber cloth was sufficient to eliminate many kinds of common bacteria. More enduring and dangerous bacteria like clostridium difficile (which can cause diarrhea or even inflammation of the colon) and flu viruses may require a sterilizing agent like bleach or alcohol, he said.

While manufacturers, including Apple, warn against using alcohol, such wipes work great at cleaning grime, muck and marks off your device. (In fact, many Apple stores are stocked with Clens wipes by Bausch & Lomb, which contain isopropyl alcohol. Apple declined to explain the contradiction.)

A Clens kit, which includes three wipes, a 3-ounce bottle of cleaning spray and a cleaning cloth, costs about $20. But it’s far cheaper to make your own.

To clean his own mobile devices, Derek Meister, a technician for the Geek Squad, Best Buy’s repair and online support service, uses a 1-to-1 ratio of 70 percent isopropyl alcohol and distilled water, which costs less than $4 to make. (“You want distilled water and purer alcohol so there are fewer chemicals or minerals left behind when the solution evaporates,” he explained.)

Never spray directly onto the device. Meister recommends filling a spray bottle with the diluted alcohol, then lightly moistening a lint-free microfiber cloth (no paper towels) and gently wiping down the screen and case. To clean corners and around ports, use lint-free foam swabs rather than cotton Q-tips.

Sanitizers, air

If you’re super germophobic, consider purchasing an ultraviolet sanitizer. Violife makes a $50 cellphone sanitizer about the size of a coffee can. Just pop your phone into the dock and replace the lid for ultraviolet light to zap pathogens. Verilux sells a $40 sanitizing wand, which the company claims kills up to 99 percent of germs when waved over your electronics. While sanitizers won’t improve the look of your device, they might spare you the sniffles.

Using a can of compressed air to blow around ports and between keys will help maintain the look, performance and value of your device. It’s also possible to buy a specialized air compressor, such as the DataVac Electric Duster, which lists for $100 and comes with all sorts of little attachments for cleaning out your crevices and seams.

“An air compressor gets things really clean and it’s environmentally good because you don’t have a little can to throw away after blowing air,” said Miroslav Djuric, chief information architect at ifixit.com, an online do-it-yourself community. Djuric uses an all-purpose compressor he bought at Home Depot and fitted with an inflating needle (the kind used to inflate a basketball or a bike tire) to precisely direct the airflow.

Screens and sleeves

Another route to cleanliness is washable screen protectors for laptops, tablets and smartphones, which are available from manufacturers such as Boxwave, BodyGuardz, iSmooth and Moshi at a cost of $5 to $40, depending on the size. They’re easy to apply (and reapply) without unsightly bubbles or impaired visibility or functionality of touch screens.

Similarly, Ultra-Sleeves and Chef Sleeves are clear, hygienic and protective iPad and tablet covers. These disposable sleeves, which enclose the entire device, are designed for people working in health care, construction, industrial or restaurant settings. But they’re also ideal for people who have to share their devices during the course of the day. A pack of 10 costs about $12.

It’s up to you how obsessively you want to clean your mobile devices, but “your mobile device is something you want to clean regularly,” said Guerrero, co-author of a study about the persistence of bacteria on iPads published this fall in the American Journal of Infection Control.

And, like your toothbrush, it’s probably not something you want to pass around the table.