Question

We all have experienced that chopping onions bring tears to our eyes. Why does this happen?

• A. Cytosine, a chemical present in onions causes irritation in the eyes.
• B. The bacteria present in the onion release a chemical that irritates human eyes.
• C. A gas from onions mixes with water in the eyes to produce an acid.
• D. Allinase, a chemical stimulant found in onions, makes our tear glands unstable.

Answer 1

The correct option is C A gas from onions mixes with water in the eyes to produce an acid.

Onions contain some chemical substances (amino acid derivatives) that form certain kinds of acids in the onion cells. When we cut an onion, substances present in the onion cells start mixing with the amino acid derivatives and produce a volatile, sulphur-containing gas. When this gas reacts with the water present in our eyes, sulphuric acid is produced.

It is this sulphuric acid which causes burning sensation in our eyes and makes the tear glands secrete tears.