Onions Make You Cry Through a Two-Step Chemical Reaction
An onion is a pungent edible bulb. Cutting one releases a chemical that forms an irritant gas when it meets the eye.
An onion is a pungent edible bulb used across almost every cuisine. Cutting one triggers a chain reaction: enzymes released by the damaged cells convert sulphur compounds into a volatile gas, *syn-propanethial-S-oxide*, which reacts with the water in your eyes to form a mild sulphuric acid. The tears are a rinse response. Chilling the onion slows the enzymes, and a sharp knife damages fewer cells, which is why both help.
- An edible bulb. *Chopped onion.*
- Spring onion — the young form. *Spring onions.*
- Shallot — a smaller relative. *A shallot.*
- Allium — the genus. *The allium family.*
- Know your onions — to be expert. *He knows his onions.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | onion | One onion. |
| Plural | onions | Two onions. |
| Adjective | oniony | An oniony smell. |
| Genus | Allium | Allium cepa. |
| Latin | unio | A single large pearl. |
- Fry the onions until soft.Cooking.
- Chilling slows the enzymes.Tip.
- He really knows his onions.British idiom.
The allium family
- Onion — the common bulb
- Garlic — cloves rather than layers
- Leek — a long stem of rolled leaves
- Shallot — smaller and milder, grows in clusters
- Chive — grown for its leaves rather than its bulb
Old French *oignon*, from Latin *unio*, which meant both a single large pearl and a kind of onion, from *unus*, one.
Why do onions make you cry?
Cutting releases enzymes that produce a volatile gas, which reacts with the water in your eyes to form a mild acid.
Does chilling an onion help?
Yes. Cold slows the enzymes, and a sharp knife ruptures fewer cells, so less of the gas is released.