Onions makes us Cry ! But why ? - the science behind it

Onions make us cry ! But why?

Whenever we start cutting onions, tears starts rolling down. Do you know why? The answer is pure biology and chemistry in action and not our emotion.😰

What’s Inside an Onion?🧅

Onions contain special molecules called sulfur compounds. These compounds are part of the plant’s natural defense system. When an onion is whole, these chemicals are safely stored in different parts of the cells.

But once you cut the onion, the cells break open — and that’s when the real reaction starts.

The Chemical Reaction That Triggers Tears

Here’s what happens when you slice an onion:

• You cut the onion, breaking open its cells.
• Enzymes like alliinase are released and react with sulfur compounds.
• This reaction forms a gas called syn-Propanethial-S-oxide.
• The gas evaporates at room temperature and reaches the eyes.
• The gas reacts with the lubricant in our eyes and creates a irritation feeling as it forms mild sulfuric acid.
• It activates the lacrimal gland and release tears to wash it away.

Watch: Why Onions Make You Cry

How to Prevent Tears while cutting Onion?

• Chill the onion before cutting to slow down the enzymes.
• Cut under running water to wash away the gas.
• Use a sharp knife to reduce cell damage.
• Wear goggles to block the gas (yes, really!).

Not all onions are equally tear-inducing. Red and white onions usually have more sulfur compounds than sweet or green onions.

Why Do Some People Cry More?

• Sensitivity to irritants varies from person to person.
• Some people’s eyes react faster and produce more tears.
• It also depends on how fresh and strong the onion is.