TIME Germs

Bumping Fists Spreads Fewer Germs Than a Handshake, Study Says

From right: U.S. President Barack Obama and First Lady Michelle Obama bump fists at an election night rally at the Xcel Energy Center on June 3, 2008 in St. Paul, Minn. during his first presidential campaign.
From right: U.S. President Barack Obama and First Lady Michelle Obama bump fists at an election night rally at the Xcel Energy Center on June 3, 2008 in St. Paul, Minn. during his first presidential campaign. Scott Olson--Getty Images

Plus, they're cooler

President Barack Obama’s famous fist bumps may have health benefits as well as a cool factor, because a new study shows that greeting someone with your knuckles is much more hygienic than shaking their hand.

Dr. Dave Whitworth, of Aberystwyth University in Wales, tested the germ-carrying potential of various greetings by high-fiving, fist-bumping, and shaking hands with with a PhD student. One wore a glove covered in bacteria, the other wore a clean glove.

They found that handshakes transferred the most germs, with high-fives transferring only half as many and fist-bumps transferring 90% less, which means that fist-bumping instead of shaking hands could help limit the spread of illness.

The study will be published in the August issue of the American Journal of Infection Control.

Dr. Whitworth hypothesized that fist-bumps are more hygienic mostly because they minimize the surface area of hand-to-hand contact, and they’re usually quicker than handshakes.

“People rarely think about the health implications of shaking hands,” he said in a statement. “If the general public could be encouraged to fist-bump, there is genuine potential to reduce the spread of infectious diseases.”

Plus, if we all fist-bump, then we’d never have to deal with that limp-fish thing again.

TIME Germs

You Asked: Is the 5-Second Rule Legit?

The Five Second Rule
Illustration by Peter Oumanski for TIME

When food hits the floor, some say you have 5 seconds to retrieve it before filth hitches a ride. Here’s what germ experts have to say about that

Donut down! You quickly grab your grub, certain you’ve satisfied the 5-second rule with time to spare. But is your fallen food safe to eat?

Past research shows roughly 70% of women would say yes, along with 56% of men, says Paul Dawson, a food scientist at Clemson University who has lab-tested the legitimacy of the 5-second rule. Unfortunately, snacking on stuff that has touched the ground is always a risky proposition, he says.

“I compare picking up dropped food and eating it to not wearing a seat belt,” Dawson says. You could drive a lifetime without wearing a safety belt and never have an accident, but that doesn’t mean you’re safe not wearing one, he explains.

Dawson and his team tested the time it takes harmful bacteria like salmonella to transfer from various surfaces—wood, tile, carpet—to either dry foods (bread) or moist ones (bologna).

Here’s what they found: The length of time food spends on the floor does increase the amount of bacteria that latches on. Also, specific food-floor combinations (especially moist food on tile) result in a greater transfer of germs. But regardless of the snack-surface specifics, a significant amount of unhealthful gunk jumps from the ground to your food pretty much instantaneously, Dawson explains.

“I stand by the zero-second rule,” he says. “If bacteria is present on the ground, it will be transferred to your food.”

Recently, biomedical scientist Anthony Hilton and colleagues at Aston University in the UK repeated Dawson’s experiment with different sickness-causing bacteria like E. coli and Staphylococcus aureus. The results didn’t change.

“The majority of bacteria transfer to the food immediately on impact,” Hilton says. “The quicker you pick up your food, the fewer bacteria will transfer.” But that doesn’t mean a speedy recovery of your fallen treat will keep you safe from germs, he adds.

What about food falling on other surfaces—like your desk at work? It all depends on whether illness-causing bacteria are present, Dawson says. According to a University of Arizona study, the average office desk harbors hundreds of times more germs than the average office toilet seat.

Consider yourself warned.

TIME Germs

Why You Should Let Kids Eat Dirt

Gardening Hands - let your kid eat dirt
Getty Images

Kids who are exposed to more germs before age one are less likely to have allergies and asthma a new study shows

Infants who are exposed to unsavory things like rodent and pet dander, roach allergens and household bacteria during their first year are actually less likely to suffer from allergies and asthma, Johns Hopkins researchers say.

A new study published in the Journal of Allergy and Clinical Immunology shows that being exposed to allergens before a child turns one can benefit allergies. To reach these findings, the researchers studied 467 inner-city infants in Boston, New York and St. Louis. They tracked their health over three years, and visited their homes to calculate the levels of a variety of allergens. They also conducted allergy tests on the children and collected bacteria from dust gathered in their homes.

The kids who lived in homes with mouse and cat dander as well as cockroach droppings during their first year had lower rates of wheezing by age 3. The kids with a greater amount of bacteria in their homes were also less likely to wheeze and were less likely to have environmental allergies.

Kids who were completely free of allergies were also most likely to grow up in homes with the highest amount of allergens and bacteria in them. In contrast only 8% of kids with both allergies and asthma were exposed to the substances by the time they were 1.

It’s possible you’ve heard of the “hygiene hypothesis,” which is the speculation that the reason Americans have so many allergies is because we are, quite simply, too clean. Kids are kept in such sterile environments that they never build immunities to common allergens.

A significant amount of research has shown that kids who grow up living on farms with livestock, or with a pet are less likely to develop asthma or allergies. Prior research has also suggested that it’s not necessarily dust that provides a protective benefit, but the microbes that are in our guts that influence our immune system and ability to fight off infections.

The new findings support a growing body of evidence that a little exposure to germs here and there never hurt anyone, and in fact, could actually be protective.

TIME Science

Science Confirms the Five-Second Rule Is Actually a Real Thing

Broken wineglass and food plate falling on table
Getty Images

It's still best to keep your food on your plate

Research at the U.K.’s Aston University has confirmed the old adage that food dropped on the floor for five seconds is clean—or at least it’s less likely to be dirty than if it sits there.

To test out the rule, students dropped toast, pasta, biscuits, and candy onto a floor that had been exposed to common bacteria and measured how much of the bacteria transferred when it was left on the surface for durations ranging from three to 30 seconds.

The results found that food left on the floor for less time does indeed get exposed to less bacteria. But more importantly, the texture of the floor that food is dropped on to is the most significant factor in how much bacteria is transferred.

Carpet is actually the cleanest surface to drop food onto, contrary to its connotations as a fibrous home for germs. It carries “the lowest risk of bacterial transfer onto dropped food,” Professor Anthony Hilton explains. Laminate and tiled floors are the worst offenders for dropped food infection.

That said, we’re not taking any chances.

(h/t Geekosystem)

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