Why Do Onions Make You Cry?

If you have ever cut an onion, it’s likely you have started to well up – and it’s not because the vegetable was so beautiful it brought tears to your eyes, nor because the knife accidentally slipped and you cut yourself. It's the onion. Onions make us cry, because they’re trying to protect themselves. We consulted with Chef Missy Smith-Chapman for what we need to know on this topic.

Why Do Onions Make You Cry?

An onion’s ability to make us cry is actually a natural defense they have to ward off being eaten by mammals, says Smith-Chapman.

“When you cut or even bite into an onion, it releases propyl sulfoxide and when it gets in your eyes, it turns into sulfuric acid,” says Smith-Chapman. “It is the sulfuric acid’s effect on nerves around your eyes that can cause pain and make you tear up.”

Your eyes begin to water, because it’s our body’s natural defense trying to wash the irritant away. While it might seem tempting to wipe away the tears, don’t do it.

“Never touch your eyes,” Smith-Chapman says. “Your hands are also covered in these sulfur compounds and you will make it worse.”

Will All Onions Make You Cry?

Because onions are masters of absorbing sulfur, all varieties have the ability to make you cry, but sweeter onions, like Vidalia onions, are less likely to make the tears flow.

4 Ways To Stop Crying When Cutting Onions

Whether you're hosting a dinner party with guests arriving or you just want to stop the waterworks that onions cause, it’s possible to stop crying when you cut them.

Use a Sharp Knife

“As a chef I was taught that a sharp knife and fresh onions are the key to not crying, because a dull knife creates a ragged cut with greater surface area, and releases more propyl sulfoxide,” says Smith-Chapman.

Open Windows

Keeping a breeze going in the kitchen can help reduce the amount of irritants in the air that impact eyes. “Open the windows, turn on the fan above your stove or use the overhead kitchen hood while you work,” suggests the American Academy of Ophthalmology. 

Chill Onions

“You can chill or add a splash of acid like lemon juice to your onions,” says Smith-Chapman. “This will help to slow down the tears by reducing the volatility of the propyl sulfoxide, as well as adding flavor.”

Wear Onion Glasses

If the windows are open, the onions have been chilled, and you’re using a sharp knife on fresh onions and you are still crying, it’s time to invest in a pair of onion goggles that will protect eyes from irritants.

Are There Ways To Cut Onions And Prevent Tearing Up?

When it comes to cutting onions, tearing up sometimes is a given, but reducing risks helps.

“Make sure your knife is sharp so you are not releasing so many tear inducing compounds,” Smith-Chapman says.