Why do onions make you cry when you cut them? How do you slice onions without tears? Are leftover onions toxic? Enjoy these onion facts—and some folklore.
Why DO Onions Make You Cry?
To put it simply, fumes from onions trigger a reaction in your eyes’ glands that starts the flow of tears. When you cut the onions, you are damaging their cell walls and causing naturally occurring amino acid sulfoxides to get released, mix with other compounds in the onion, and turn into a gas that wafts into your eyes, causing irritation. Your tears are your eyes’ efforts to wash away the irritant.
How to Slice Onions Without Crying
There a few tips and tricks to reduce the tears.
- Put the onion in the freezer for a few minutes before slicing. This slows down the conversion of the acids into irritating gases.
- Skewer a small piece of bread onto the cutting knife, pushing it right up to the handle; the bread will absorb the odors from the onion as you are cutting it.
- Hold a slice of bread lightly between your teeth while chopping onions. This sounds silly, but it works! The bread will absorb some of the gases as they waft toward your eyes.
- Cut an onion properly. See how to cut an onion in four easy steps.
Are Leftover Onions Poisonous? No.
There’s a myth floating around that says once an onion’s been cut, you have to use it all and eat it right away; otherwise it can poison you. It’s widely debunked by food-safety experts.
Where did this idea come from? It may have roots that go back to the 1500s, when people believed that scattering pieces of cut onions around the house would protect them from bubonic plague. That myth has morphed into a still-circulating belief that raw onions act as “bacteria magnets,” that attract bacteria and viruses from the environment, and hence render them dangerous to eat. They aren’t. (By the same token, raw onions strewn around your indoor environment won’t protect you and your family against the flu.)
Of course, myths start with a good reason and onions really are healthy for you! Even the onion skins are high in antioxidant, anti-inflammatory properties. See my short post abut onion skins for health and more.
You can contaminate fresh onions if you prepare them with dirty hands or on a cutting board already contaminated by raw meat or chicken juices. But if you prepare the onions with squeaky-clean hands on a sanitized cutting board, it’s safe to wrap, refrigerate, and use them later.
Summer brings on picnics, barbecues, and big outdoor reunions that feature plenty of food-safety hazards. Get all the up-to-date food-safety facts—and enjoy your onions!