Tag Archives: cry

Why do onions make you cry?

Onions are one of the few truly global foods, with every major cuisine using the onion as a key ingredient. This means that millions of people are reduced to tears when preparing this hardy vegetable, but why? There’s some chemistry behind this delicious vegetable and why it makes you cry.

The culprit. Image credits: Colin

Sulfuric acid in your eyes

When onions grow, they absorb sulfur from the soil to form amino acid sulfoxides. When you cut into an onion, you slice open the onion’s cells causing their insides to pour out, along with all these substances. These sulfoxides then react with enzymes to form sulfenic acid. It is quite unstable and rearranges to form syn-propanethiol S-oxide, a combination of sulfuric acid, sulfur dioxide and hydrogen sulfide. A lot of un-unpleasant substances!

This gas drifts up to the eyes of the cutter and makes contact with nerve-endings on the surface of the eye. Nerves recognize it as dangerous and interpret the contact as a burning sensation, so the tear response reflexively makes tears to combat the irritation.


The contents of these onion cells are what makes you cry. The amino acid sulfoxides responsible for making you cry are absorbed from the earth when the onion grow. Interestingly, it is the same substance that gives the onion its taste. Image credits: Umberto Salvagnin

Cooked onions don’t hurt

Cooking the onion inactivates the enzymes so that it doesn’t irritate your eyes while you are cooking or enjoying your meal. The sooner you cook it, the sooner it stops hurting.

The cooking part isn’t so bad. Image credits: DocteurCosmos

What can you do?

No one likes crying, and if you do have some reason to cry, it definitely shouldn’t be onions. There are many different strategies to try if you are tired of weeping every time you are trying to make French onion soup. They all revolve around keeping the sulfuric gas from reaching your eyes.

  • Block the gas completely. You can wear regular or fancy safety goggles, but make sure that they are sealed at the sides.
  • Slow down or inhibit the reactions that create the irritating compound. Freezing the onion for 15 minutes or keeping it in the refrigerator results in a sting-free cutting experience.
  • Re-direct the irritating gases. Cutting under running water works though it is rather logistically difficult. A more practical method is to turn on the kitchen stove vent and cut under it.
  • Draw out the sulfuric compounds from the onion. Soaking the onions in water for 15 minutes works but causes the onions to lose some flavour.
  • Buy different onions. Sweet onions, scallions, and red onions cause less irritation while white onions are the worst at making you cry because they absorb more sulfur from the soil.

Other old wives’ tales that that do not hold up in practice are lighting a candle and chewing gum while cutting.

So, there you have it – why onions make you cry, according to science, and how you can stop it. Bon appétit!

New reserach suggests mammals are tunned to the crying calls of infants, even when these don't come from members of their species. Photo: Flickr Commons

The primal call: mammals may respond to baby cries even when they’re from another species

New reserach suggests mammals are tunned to the crying calls of infants, even when these don't come from members of their species. Photo: Flickr Commons

New reserach suggests mammals are tuned to the crying calls of infants, even when these don’t come from members of their species. Photo: Flickr Commons

Crying is a baby’s principal means of communicating its negative emotions, yet no matter how annoying and painful it may be to hear those high pitched screams, humans are naturally drawn to this call. Well, it seems our brains are hard-wired to respond strongly to the sound, making us more attentive and priming our bodies to help whenever we hear it. A new study by biologists at the University of Winnipeg, Canada suggests that this isn’t a solely human trait. Their findings suggest there’s a common element among the cries of most, if not all mammalian species that draws adults to investigate as a primal instinct, ignoring any risks in between.

The call

Susan Lingle, a biologist at the University of Winnipeg, and colleagues recorded the calls made by infants from a variety of mammal species when separated from their mother or otherwise threatened. These were then played our in the Canadian prairies from hidden speakers to wild mule deer (Odocoileus hemionus). The researchers noticed that mother deer quickly moved towards the source of the sound when the cry of an infant deer was played, but same held true whether the cries came from infant fur seals, dogs, cats or humans. All these species call at roughly the same high pitch. Even the ultrasonic calls of infant bats attracted the mother deer, of course after being tuned to a lower frequency using software.

The findings suggest there’s a common acoustic element that some mammals are hard-wired to respond to and investigate, at the cost of taking risks. It may be that this common element was kept across species, even in those whose lineages separated more than 90 million years ago.

“These are calls that are generally made in a life-or-death situation,” Lingle says. “I think the advantage of securing survival for your offspring outweighs the potential for error.”

Findings appeared in the journal American Naturalist.