What Can Happen If You Don’t Wash Your Lettuce?

Now that the summer season is here, it’s prime salad-making time. But while prepping your greens, it’s tempting to skip over the step of washing your lettuce. That’s especially true if you purchased pre-washed greens — many even clearly state on the label that they’ve been bathed several times, after all. But food safety and microbiology experts say you’re rolling the dice if you don’t wash your lettuce before you eat it. 

“Washing is an opportunity to decontaminate the lettuce,” says Thomas Melendy, Ph.D., associate professor of microbiology and immunology, and biochemistry at the University at Buffalo. But there’s so much more to it than that. Here’s why doctors say giving your greens a rinse is crucial. 

What are the risks of not washing your lettuce?

A few things, actually. We can generally divide them into two camps: the ick factor and the stuff that will make you sick. On the gross side, it’s important to consider that there can be a lot of stuff on your lettuce. That includes soil, sand, and general debris, along with bugs.

"[Washing] helps remove dirt and pesticide residues as well," says Wade Syers, DSocSci, extension specialist for food safety at Michigan State University Extension. If you don’t give your lettuce a good rinse, there is a solid chance any of those could wind up in your mouth. 

But while those factors might be disgusting, there are also important health reasons for cleaning your lettuce.

“Based on epidemiological data of a number of outbreaks, enterohemorrhagic E. coli and Cyclospora are the greatest concerns,” says Francisco Diez-Gonzalez, Ph.D., director of the Center for Food Safety at the University of Georgia.

In case you’re not familiar with these bacteria, both put you at risk for developing uncomfortable symptoms like diarrhea, fever, and stomach cramps, per the Food and Drug Administration (FDA). If you fall into a high-risk category, like being very young, an older adult, or having a condition that makes you immunocompromised, these bacteria can make you seriously ill and can even be deadly. 

“Listeria is also a potential risk,” Diez-Gonzalez says. Like E. coli and Cyclospora, listeria can cause diarrhea and fever, along with flu-like symptoms, according to the Centers for Disease Control and Prevention (CDC). 

A big issue with lettuce is that it’s not usually cooked, which is a step that will often kill bacteria that may be lurking in food.  “All you have is washing,” says Melendy. 

It’s important to point out that lettuce can be contaminated during any step of the growing process, and it may not be lingering on the surface of your greens. “Washing may not eliminate all pathogen contamination,” says Diez-Conzalez.

Benjamin Chapman, PhD, food safety expert and department head of Agricultural and Human Sciences at North Carolina State University, agrees. “At most, you might get a 90% reduction in a pathogen that's on a leafy green leaf from washing,” he says. “It doesn't equate to using a thermometer to check the temperature when you cook meat.”

Still, experts say washing your greens can help. 

What about pre-washed greens?

Pre-washed greens have been handled more than their freestanding counterparts, which raises the risk of contamination, Melendy says. “Some outbreaks have been associated with bagged salads, which have been washed by the manufacturer most of the time,” Diez-Gonzalez points out. 

Washing pre-washed greens is unlikely to be helpful if they happen to have been contaminated during the growing process — as in, via the soil or irrigation water, says Diez-Gonzalez. But giving them a rinse can help you hedge your bets. 

Consider this, too, per Melendy: Getting sick from being exposed to these bacteria is a numbers game. “One or two bacteria or virus particles are not going to make you sick,” he explains. Instead, your immune system is likely to target those and take them out before you feel the effects. “The idea is that by washing the lettuce, you’re getting rid of the majority of the bacterial load and dramatically reducing the likelihood that you’ll get sick,” says Melendy. 

Still, you don’t need to wash your pre-washed lettuce. The FDA clearly states that many pre-cut, bagged, or packaged produce items are pre-washed and ready-to-eat, with clear labeling on the package. The FDA also adds this note: If you choose to wash pre-washed lettuce, just make sure it doesn’t come into contact with unclean surfaces or utensils.

For what it’s worth, even some food safety experts don’t wash their pre-washed lettuce. “It’s already removed more than I could remove in my kitchen,” says Chapman. “When I buy pre-washed lettuce, I open the bag and use it.”

Timing is important, too

You may have realized that washing your lettuce well before you plan to eat it can make it soften. This also can invite bacteria and bugs in, defeating the purpose of the original rinse. That’s why Melendy recommends washing your greens right before you plan to use them, and paying close attention to the use-by date, if your lettuce has one. 

“The earlier you use the lettuce, the better,” he says. “As time goes on, any bacteria in there will proliferate and you start to lose that numbers game.”