For those of you who often cook in the kitchen, you are likely familiar with the task of cutting onions. When cutting onions, your eyes may experience a burning sensation that makes you cry. What causes the burning sensation while peeling onions, and how can you prevent it?

Why onions make you cry?

Onions are a staple in many kitchens, used not only to add flavor to dishes but also for their numerous health benefits. However, cutting onions, especially yellow onions, can often cause stinging eyes and tears.

The tears usually start 30 seconds to 5 minutes after you begin chopping. The longer you cut, the more intense the sting becomes, leading to more tears.

Onions are rich in sulfur compounds. Their cells contain amino acid sulfoxides, which produce sulfenic acid. This sulfur compound protects onions from pests, such as rodents, while they are growing in the ground.

Cutting into an onion causes damage to its cells, resulting in the release of enzymes and sulfenic acid. These substances combine in the air to form propanethial S-oxide, a gas that irritates the eyes. When this gas reaches your eyes, it triggers a reaction that makes your eyes produce tears to flush out the irritant.

Interestingly, this does not occur when onions are cooked because heat deactivates the enzymes, preventing the formation of the irritating gas.

How to soothe stinging eyes when chopping onions

Although eye irritation from chopping onions is not harmful, it can be very uncomfortable. Here are some ways to soothe your eyes:

• Rinse your eyes with clean, cold water
• Apply a cold compress, or place cold cucumber slices or cotton balls soaked in cold water over your eyes to reduce irritation
• Use eye drops to rinse and refresh your eyes

How to prevent tears when chopping onions 

To avoid tearing up while chopping onions, try these tips:

• Chill the onions: Refrigerate the onions for 10–15 minutes before chopping. The cold slows down the enzymes, reducing the amount of irritating gas released
• Soak onions in water: Soak onions for 30 minutes before chopping. The water absorbs some of the gas, reducing its potency
• Use a sharp knife: A dull knife crushes the onion more, releasing more gas. A sharp knife makes cleaner cuts and minimizes gas release
• Cut in a well-ventilated area: Chop onions near an open window, under a range hood, or beside a fan. The airflow helps disperse the gas away from your eyes
• Wear safety goggles: Protect your eyes by wearing goggles while chopping onions
• Avoid touching your eyes: Be sure to wash your hands thoroughly with soap and water after handling onions to avoid transferring any irritants to your eyes

Crying while chopping onions, particularly yellow onions, is caused by an irritating gas that stings your eyes. While not dangerous, it can be extremely uncomfortable, so it is best to take precautions to prevent or minimize the irritation. If your eye irritation persists, consider consulting a doctor.

If you need medical advice or consultation, you can either visit a doctor or make use of the consultation features that are available in the Ai Care application by downloading the Ai Care application from the App Store or Play Store.

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