This Is the 1 Reason Why You Should Never Double-Dip Your Food

guacamole and chips

Certain food habits dramatically increase your exposure to germs. | Fudio/iStock/Getty Images

We’re surrounded by bacteria, but that doesn’t stop us from getting grossed out by certain foods or by the germs lurking in our kitchens. But there are a few gross food habits that can also increase your exposure to bacteria — and up your risk of getting sick. Habits like double-dipping your chips or sharing a bowl of popcorn are some of the germiest and grossest things you can do while eating a snack.

Below, check out the reason why you should never double-dip your food — or order lemon in your water, or follow the five-second rule when you drop something on the floor.

Gross food habits can increase your exposure to germs

CNN reports that Paul Dawson, a food scientist and professor at Clemson University, conducted a study on how common food habits can spread bacteria and germs. The risk of getting sick from eating salsa when somebody else has been double-dipping, or eating a slice of cake at a birthday party is pretty low. But the risk still isn’t zero. Some of the most common food habits can increase your exposure to germs and bacteria.

Double-dipping spreads germs into shared food

veggies with dip

Double-dipping increases bacteria levels in the dip. | iStock/Getty Images

Whether we’re talking about dipping chips into salsa or bread into cheese fondue, double-dipping is a pretty gross snacking habit. Dawson and his team put chips in three types of dip with different pH levels and consistences: salsa, chocolate syrup, and queso. They didn’t find any mouth bacteria in the dips when people dipped chips only once. But when they double-dipped, the researchers found much higher bacterial populations.

Interestingly enough, the type of dip matters. Salsa subjected to double-dipping had five times more bacteria than chocolate or cheese in which people had also double-dipped. Dawson explains that that’s probably because salsa falls off your chip and back into the bowl, instead of sticking to the chip. Meanwhile, chocolate syrup and cheese dip are more likely to stay on the chip — and transfer less bacteria. 

Asking for lemon in your water is a major mistake

water with lemon

The lemon probably isn’t free from harmful bacteria. | iStock/Getty Images

The next time your server asks you if you’d like a slice of lemon in your water, you should definitely say no! Many restaurants leave lemons sitting in open containers at room temperature. Some restaurants even refrigerate them overnight to reduce waste. Many food workers don’t have clean hands when they handle lemons, and depending on where ice is stored, it can pick up bacteria, too.

Dawson tested the rate of bacterial transfer to both lemons and ice using E. coli. 100% of the bacteria transferred to wet lemons, but only 30% transferred to dry lemons. For the ice, an average of 19% of the bacteria on hands transferred, and 66% of bacteria on an ice scoop transferred. The bacterial population only increased on lemons contaminated with E. coli and left at room temperature, and even the bacteria on refrigerated lemons survived.

Even handling the menu exposes you to germs

woman looking at menu

Restaurants often don’t sanitize the menus. |

Most people wouldn’t dream of eating at a restaurant without checking out the menu. But as CNN reports, restaurants don’t often sanitize their menus. And menus can actually spread germs and bacteria around the restaurant. Dawson collected random samples of local restaurant menus and tested them for bacteria. The researchers found low numbers of bacteria living on the menus.

However, they found that at busier times in the restaurants, the menus had higher numbers of bacteria than at quieter times of the day. When the researchers contaminated the menus with E. coli, about 11% of the bacteria transferred to people’s hands. Only low amounts of bacteria could survive on the menus over a period of one or two days.

Sharing popcorn exposes you to germs — but not quite as many as you’d think


Popcorn might be relatively safe, though it still transfers germs. | iStock/Getty Images

Most of us don’t think twice about sharing a bag of popcorn at a movie or a carnival. The Clemson University researchers tested how gross this habit really is. You probably shouldn’t share popcorn if you don’t want to be exposed to any germs. But sharing popcorn, surprisingly enough, seems to carry only a low risk of bacterial transmission.

As CNN explains, Dawson and his team spread a non-infectious E. coli strain on people’s hands. Then, they measured how much transferred to the popcorn they picked up, and the popcorn left in the bowl. The bacteria did transfer, both to the popcorn in their hands and the popcorn left in the bowl. However, the rate of transfer reached just 0.2% and 0.0009%. And out of 136 tests, 24 resulted in no bacterial transfer at all.

The 5-second rule doesn’t work

Dropped ice cream

It’s not a good idea to eat any food that’s been on the floor. | iStock/Getty Images

Everybody’s heard that if you drop your food on the floor and pick it up within five seconds, you can still safely eat it. But that’s not what the Clemson University researchers found. They spread salmonella bacteria on tile, carpet, and wood. Then, they tested what happened if they dropped bologna or bread on the floor, and picked it up after five seconds.

“There was enough bacterial transfer in five seconds that from a practical standpoint, it’s not a really good idea to eat food from the floor,” Dawson told CNN. Another study, this one by a food microbiologist at Rutgers University, also found that there’s “no safe amount of time” for food to be left on the floor. The type of food and the kind of surface influence the amount of bacteria transferred. Wet foods prove more likely to pick up bacteria, and carpets prove less likely to transfer bacteria.

Blowing out the candles on a birthday cake definitely transfers germs

rainbow birthday cake

You’re blowing all your germs on the frosting. | iStock/Getty Images

Most people love the tradition of blowing out the candles on a birthday cake. But blowing out the candles can actually spread bacteria from your mouth to the cake. Yuck! According to CNN, Dawson discovered that when you blow out the candles on a cake, the frosting ends up with 15 times more bacteria than it had before.

Want to know how the researchers came up with that number? They ate some pizza (to simulate a birthday party and activate the salivary glands). Then, they spread frosting on foil and placed it in top of a Styrofoam disc with 17 candles. After they blew out the candles, they measured the number and type of bacteria in the frosting. The amount of bacteria will vary based on how “sloppy” someone is when they blow out the candles. But bacterial transfer does happen, and can even make you sick if the person blowing out the candles is “carrying a disease.” 

Playing beer pong exposes you to tons of bacteria, too

beer pong game

All the bacteria on the ball will end up in the cups. | MikeyGen73/iStock/Getty Images

Even if you don’t play beer pong yourself, you might want to discourage your favorite college students from taking part in the popular game. (For those who need a refresher, the game involves throwing a ping pong ball across a table, aiming for a plastic cup filled with beer. If the ball goes in, your opponent has to drink the whole beer.)

The problem is that ping pong balls are often covered in bacteria, especially after bouncing on the table, falling on the floor, and changing hands numerous times. Dawson found the highest levels of bacteria, predictably enough, on ping pong balls that had been used outside. He also found that nearly all of the bacteria on a given ping pong ball will transfer to the beer. 

Most bacteria won’t hurt you

Sick man with thermometer in mouth

Whether you get sick depends on the type of bacteria. |

These gross food habits will expose you and your friends or family to some extra germs. But how much of that bacteria can actually hurt you? As CNN reports, Dawson explains that “risk is often dependent on the type of bacteria. And that mostly depends on where the bacteria came from.”

The kind of bacteria you’re exposed to depends on the health of the people you’re sharing your food with. If someone is sick, they may have infectious bacteria in their mouths. So blowing out the candles on a cake or sharing a bowl of salsa can spread pathogenic bacteria. But under normal circumstances, your chances of contracting a disease through one of these food habits is actually pretty low.

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