The Real Reason You Tear Up Around Onions

If you've ever chopped or sliced an onion, you have probably noticed your eyes burn and tear up. Why are onions making you cry? Onions grow underground, but that doesn't stop wildlife, insects, fungi, and bacteria from chowing down. According to Science News For Students, onions may have developed the chemical reactions that cause your eyes to burn to keep predators like these from eating them. 

Scientists have been trying to determine how onions cause this reaction for 40 years. They initially thought it was alliinase, an enzyme that helps create the chemical reaction that converts sulfoxides in the onion into tear-inducing molecules. But, when Japanese scientists were trying to make a tearless onion, they discovered alliinase wasn't the trigger for the chemical reaction; it was likely LF synthase.

What makes you cry when you chop onions is a chain of chemical reactions that releases a gas containing sulfur. That gas turns into sulfuric acid when it makes contact with your eyes and causes burning, itching, and tears. Your eyes tear up to flush out the irritant. 

How to reduce the tears from onions

Onions are beneficial to your health, so don't cut them from your diet. There are some things you can do to keep onions from making you cry. A dull knife will cause more damage to the onion, releasing more of the gas that makes you tear up, so make sure your knife is sharp (via Healthline).

You might also want to try using water. Soak your onion in an ice bath for 30 minutes before cutting into it, which might reduce the sulfuric acid compounds. Some swear by chopping onions while they are submerged in water. Pat these onion slices or cubes dry with a towel before cooking them, so the oil doesn't sizzle out of the pan and onto you.

There's also the option to wear goggles while cutting an onion to stop the irritant from getting to your eyes. Good air circulation can also help. Turn on your hood fan, chop your onions under that, or turn on a box fan in the kitchen.

You can also use other vegetables in the onion family, like garlic, scallions, shallots, chives, or leeks. You can also find prechopped onions in your grocery store's freezer section. They don't taste the same as fresh-cut onions, but you won't be crying.