• By Jeff Olsen

Mayo Clinic Minute: Why do onions make you cry?

October 9, 2017

Cut up an onion, and you’ll likely cry a few tears. It’s the result of a chemical reaction you start with the first slice of your knife – a reaction that researchers continue to explore.

Jen Welper, executive chef with the Mayo Clinic Healthy Living Program, says the sting is part of the onion’s survival mechanism, and a stiff upper lip is the best way to beat it.

Watch: The Mayo Clinic Minute

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Not long after the cutting comes the crying.

"The irritant can be pretty strong and make us cry pretty quickly," says Welper.

That irritant is actually part of the onion’s built-in protection against predators. Chopping breaks up cells inside the onion and sets off a chain reaction that releases volatile chemicals. When those chemicals hit our eyes, your eyes well up.

"It activates our tear glands," explains Welper. "And, then, we cry."

Welper has heard about plenty tricks to thwart the tears: Hold a piece of bread in your mouth, wear goggles ….

"Rinse the onion under cold running water," continues Welper. "Another one is to, like, light a match, and blow it out."

Welper says it all sounds like more work than it’s worth.

"Just cut the onion, and get it over with," she laughs.

Welper says you can reduce the amount of irritant that gets to your eyes by keeping your onion together as much as possible as you cut it.

"I hold just the piece that I cut, pull my knife out,” says Welper, demonstrating how she cuts an onion.

And if you end up shedding a few tears?

"Sometimes it’s really therapeutic to have a good cry," she says. "So just let it out."

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