Lettuce, spinach, and bagged salads may be nutritious, but they’re not always as safe as you might think. Leafy greens are a leading source of foodborne illness in the United States, responsible for an estimated 2 million illnesses each year, according to a 2024 study.
With the Centers for Disease Control and Prevention recently scaling back a key foodborne illness monitoring program, you might be wondering: Does the usual advice—like rinsing your produce—actually help prevent you from getting sick from leafy greens?
“Leafy greens are often linked to foodborne illness because they can pick up germs at so many stages before they reach your plate,” Jessica Gavin, CFS, CCS, a certified food and culinary scientist, told Health.
On the farm, factors like contaminated irrigation water, manure used as fertilizer, nearby livestock, or wild animals moving through fields can introduce bacteria like E. coli and Salmonella. (Spinach and lettuce are especially vulnerable because they grow so close to the soil, she said.)
“The larger the field is, the less likely it is that it’s being monitored closely,” said Bryan Quoc Le, PhD, a food scientist and author of 150 Food Science Questions Answered. Specialty greens, like arugula, are more often grown on smaller commercial fields, “meaning workers will have a better handle of what’s going on there,” he added.
After harvest, additional steps like washing, chopping, processing, and packaging can spread contamination even further, as more hands and equipment come into contact with the greens.
Research suggests that washing your leafy greens may reduce most pesticide residue. It can also remove dirt, debris, and some bacteria from the surface, Gavin said.
But a thorough rinse can’t get rid of all germs. “The vast majority of pathogens adhere to the surfaces of [greens], and it’s very, very difficult for water to penetrate this and remove them,” said Quoc Le.
The shape of leafy greens also doesn’t do it many favors. Microbes like E. coli can “hide in tiny crevices, or even get inside the plant tissue, where rinsing won’t reach,” Gavin added.
Pre-washed greens, like those in salad kits, aren’t immune to these issues. Not only can bacteria still cling to the lettuce, but increased handling and processing can raise the risk of contamination. Listeria is a particular concern because it can survive on processing equipment and continue to grow at refrigerator temperatures, according to Gavin.
The only foolproof way to fully kill bacteria on your greens, per Gavin? Cook them.
Even though rinsing greens can’t eliminate all germs, it can help remove some—and there are other good reasons to give them a wash.
For the best chance of reducing contaminants, Gavin recommends the following steps:
- Wash your hands and clean any counters, sinks, and tools you’ll be using with hot, soapy water to prevent cross-contamination.
- Soak the leaves in a clean bowl of cold water to loosen visible debris. (Cold water keeps your greens crisp, whereas hot water can cause wilting, open pores, and let bacteria in.)
- Separate and rinse the leaves under cool, running water for about 30 seconds, discarding any torn or bruised pieces.
- Dry using a salad spinner or clean paper towels.
- Rinse again for about 30 seconds.
- Dry thoroughly using a salad spinner or clean paper towels.
While washing your leafy greens can help remove pesticides, dirt, debris, and some bacteria, it can’t completely eliminate germs. That’s because certain bacteria tend to cling to leaves and hide out in crevices. Still, that doesn’t mean you should skip rinsing—try running the leaves under cool water for about 30 seconds, drying them, and then rinsing again.
