Gadget shops

While you're playing around on that new smartphone, you could be picking up germs from the thousand people who tested it out before you. "Most stores do clean their equipment," says Tierno, "but they certainly don't clean after each use."

A study published last year in the Journal of Applied Microbiology found that viruses easily transfer between glass surfaces (think iPad or smartphone faces) and fingertips. And a recent report found that of four iPads swabbed in two Apple stores located in New York City, one contained Staphylococcus aureus, the most common cause of staph infections. That's not even counting the cold and flu germs that might be lurking.

Protect yourself: Before you try out the latest gizmo, quickly wipe it down with a disinfecting wipe. And (yes, once again) use a hand sanitizer after you're done.

More from Health.com: How to stop a cold in its tracks

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