Should You Wash Onions Before Using Them?
Here's what the experts say about washing your onions before using—and what food editors do in real life.
Whether it’s slicing an onion for a sandwich or dicing up pieces for stir-fry, I’ve never washed an onion in my life. A poll of the Simply Recipe editors found that none rinse their onions before peeling and using them. Is that OK?
Not really, says Rui Huang, Ph.D., a visiting postdoctoral research associate at the University of Illinois Urbana-Champaign and member of the Institute of Food Technologists’s fruit and vegetable products division.
“It is important to wash onions before peeling and using them,” says Huang. “Because washing onions first under running water can prevent dirt and bacteria on the outer skin from transferring to the flesh when peeling onions.”
The U.S. Food and Drug Administration recommends washing all produce thoroughly under running water before preparing or eating it.
Huang cautions that there could be bacteria in the soil where onions are grown, which can then spread to the onions. “So, the outer skin of onions can be contaminated with a variety of bacteria,” Huang says. “The bacteria that can cause foodborne illness are of the most concern.”
However, not all experts agree that onions must be washed before slicing.
Peel the Onion First
“Why would you?” says microbiologist Jason Tetro, host of the Super Awesome Science Show and author of The Germ Code and The Germ Files. “That skin is essentially like a peel. You don’t wash your peeled bananas or oranges or lychee fruit. Now, if you want to use a little water to rinse that slimy layer off, that’s OK. But that’s more logistics than safety.”
He says the risks are minimal as long as you peel them first. Removing the outer layers helps keep any bacteria from being pushed through to the inside.
“Peel them before you cut them,” Tetro suggests. “Like Shrek, those layers can hide all sorts of unexpected surprises. Best to get rid of them before you put a knife through it.”
How To Safely Store Onions
For the freshest onions, smart storage is key. Store onions in a cool, dry place like a pantry or basement. Keep them in a mesh bag or wire basket—anything that encourages good airflow.
“A cool, dry place is always the best,” says Tetro. “This will prevent microbial growth as well as keep the onions from dehydrating. Keeping them between 40°F and 50°F will help them stay usable for up to a year.”
Though Huang recommends washing an onion before cutting it, he says not to wash or rinse an onion before storing it. "Moisture from washing can cause onions to develop mold, spoil, and sprout during storage.”
