Why Does Chewing Gum Prevent You from Crying When Chopping Onions?

An unstable chemical in the onion is what causes us to cry.

Cutting onions and crying are two activities that are directly linked through experience and anecdote. Chewing gum while cutting onions is one of many techniques to prevent tears. A little knowledge of anatomy and chemistry is necessary to understand why.

Where Do Tears Come From?

When we cry, the tears do not actually come from our eyes. They come from small glands located next to the eye itself. Located in the corners of our eyes, the lachrymal glands produce tears when irritated.

Unstable Chemicals

Onions contain an unstable chemical known as syn-propanethial-S-oxide. When an onion is cut, this chemical is released into the air. It irritates the lachrymal glands, causing them to excrete tears.

Chewing Gum

Chewing gum while cutting onions prevents tears by forcing you to breathe through your mouth. This disperses the irritant so that a significantly smaller amount reaches the lachrymal glands, preventing them from being irritated enough to release tears.

References

• Library of Congress: Why Does Chopping an Onion Make You Cry?