Where does this come from, and can I check it?

Chopping onions releases a gas that reacts with eye moisture to form mild acid. The figure is taken from Encyclopaedia Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a food fact?

Yes. It sits on the Food shelf, one of 1,090 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

What else can I read about it?

The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

Onions produce a volatile chemical that induces tears

Chopping onions releases a gas that reacts with eye moisture to form mild acid

Slicing through onion cells releases enzymes that break down amino acid sulphoxides into syn-propanethial-S-oxide. This volatile gas diffuses through the air and contacts the moisture in the human eye, triggering tear glands to produce tears as a protective mechanism. Chilling onions before cutting slows down the enzymatic reaction.

Red Onions photograph — Gaurav Dhwaj Khadka · CC BY-SA 4.0 · licence · source

Where this comes from

Encyclopaedia Britannica

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

Go further

Food & Cooking trivia Science trivia

More facts like this

Brief boiling inactivates enzymes that degrade vegetablesScalding vegetables in boiling water preserves bright colour and crisp texture Mustard only becomes hot once it meets cold waterEnzymes in the crushed seed need water to produce pungent isothiocyanates Horseradish loses its bite in hot liquidHeat deactivates the enzyme that creates its volatile heat Digestion of carbohydrates begins inside the mouthSalivary amylase enzymes break down complex starches during chewing Enzymes act as highly specific biological catalystsActive site shapes fit target substrates precisely to accelerate vital biochemical reactions Kneading dough develops a stretchy gluten networkHydrating wheat proteins allows gliadin and glutenin to link into elastic dough

Tags: onion, enzymes, vegetables

Onions produce a volatile chemical that induces tears: the short answers

Where does this come from, and can I check it?: Chopping onions releases a gas that reacts with eye moisture to form mild acid. The figure is taken from Encyclopaedia Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a food fact?: Yes. It sits on the Food shelf, one of 1,090 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.