Why does cutting onions make you cry?

It’s such a common occurrence that even children watching cartoons are familiar with it: you cut up an onion and your eyes start to burn as tears stream down your face. But what is happening, and is there anything you can do to stop it?

Why am I crying?

As you cut into an onion, chemicals are released, which form sulfenic acids. These acids then mix with other enzymes to produce a chemical irritant called propanethiol S-oxide. This sulfuric compound reacts with the water in your tears, causing your eyes to burn, which in turn stimulates them to release more tears and wash the irritants away.

How can I stop it?

Things that help:

• Cutting onions under a kitchen vent or fan
• Freezing the onion prior to cutting it
• Cutting onions under running water or completely submerged
• Wearing goggles

Things that don’t help:

• Lighting a candle
• Holding a piece of bread in your mouth
• Holding a lit match in your mouth
• Covering the knife in lemon juice
• Heating up the onion
• Breathing through your mouth

What should I do if I’m still crying?

If your proactive measures don’t work and you find yourself with burning eyes, don’t rub them. You’ll only make them worse, especially if you have the same chemicals on your hands. Instead, rinse your eyes out with cold water, as that will flush out the irritants.

If your eyes are irritated and aren’t getting better, don’t hesitate to call one of CEENTA’s ophthalmologists. They will provide you the care you need to see clearly the next time you prepare a meal.

This blog is for informational purposes only. For specific medical questions, please consult your physician.