Myth: It's safe to follow the 5-second rule
Verdict: Fiction. It's probably not safe to eat anything that's been on the floor for even 1 second. In a recent experiment, food scientists contaminated several surfaces with Salmonella. They then dropped pieces of bologna and slices of bread on the floor for as little as 5 seconds (and as long as 60). In 5 seconds, both the bread and the bologna picked up an alarming 1,800 types of bacteria. So unless you sterilize your floors on an hourly basis, don't eat anything your shoes have touched, too.

Myth: Double-dipping spreads germs from one chip to another
Verdict: Fact. Although this social faux pas may feel dated -- Seinfeld's George Costanza is the most famous double-dipper'swiping a chip into dip, taking a bite, and then dipping the same chip again, is, in fact, a very effective way to spread germs. Having settled the 5-second rule debate, those same intrepid food scientists, using Wheat Thins and various dips, found that a double-dip deposited thousands of saliva bacteria into the dip. Of those, 50 to 100 were later transferred through the dip to a clean cracker, presumably destined for another guest's mouth. In short: Eating from a dip after someone has dipped twice is basically the same as kissing that person.

Cell phones can interfere with medical equipment
Verdict: Jury's Out. There's a chance that a cell phone call made in the wrong spot in a hospital can cause ventilators, syringe pumps, or even pacemakers to pulse incorrectly, according to a 2007 Dutch study. The researchers tested cell phones, including PDAs that use wireless Internet signals, just a few centimeters from devices; 43% caused electromagnetic interference with critical care equipment -- and a third of those instances could be potentially life-threatening to patients. Though a similar study didn't yield these same results, if you want a clear conscious, use a designated cell phone area.


Cracking your knuckles can cause arthritis
Verdict: Fiction. This nervous tic may be annoying, but it's not likely to cause arthritis. One study at the former Mount Carmel Mercy Hospital in Detroit compared 74 people (age 45 and older) who had been chronic knuckle crackers for decades with 226 who always left their hands alone. Researchers found no difference in the incidence of osteoarthritis between the two groups. But there are reasons to stop this cringe-inducing habit: The same study found that knuckle crackers are much more likely to have weaker grip strength and greater hand swelling, both of which can limit dexterity.