When you cut an onion, your eyes may begin to burn and tears may fall down your face. The tears you shed while chopping onions are not the result of any emotion. They are reflex tears caused by irritant exposure. Onions are bulbs that mature underground. They have a defense mechanism that protects them from hungry animals as they grow. When the skin of an onion is broken, it exudes enzymes and sulfenic acid. When these compounds react, they form propanethial S-oxide, an irritant gas.
Propanethial S-oxide is a lachrymatory agent, which means it causes tears to form when it comes into contact with the eye. When propanethial S-oxide comes into contact with the water layer that covers and protects your eyes, it converts to sulfuric acid. However, your eyes, like onions, have a defense mechanism that protects them from harm. When the nerves in the eyes detect a lachrymatory agent, tears are produced to flush it out. Some people cry more easily than others when they cut onions. If you are sensitive or allergic to onions or other alliums, your reaction may be more severe, resulting in symptoms such as hives, itching, and tingling.
Certain varieties of onions, especially sweet onions, are less sulfurous than others and are thus less likely to burn your eyes. White, yellow, or red onions are also more likely to make you cry than green ones. To avoid crying while cutting onions, make sure to cut them properly. Slice your onions away from you and avoid cutting them near the root end as this is the part that contains the highest concentration of sulphuric compounds that can make you cry. Chilling your onion in a bowl of ice water for 30 minutes before cutting, or cutting the onions while submerged in cold water, may help to alleviate the sting. You can also freeze or refrigerate onions before you chop them. This slows down the enzymes responsible for the series of unfortunate chemical events. Always protect yourself from the vapor.
If you experience burning and redness in your eyes after cutting onions, you may try these tips to reduce discomfort:
- Rinse your eyes with cool and clean water.
- Place a cool compress or cool cucumbers over your eyes to help reduce irritation.
- Use lubricating eye drops to flush out the eyes.
ZDN DMO II Rowence F. Zorilla, RND
References:
1. Why Do Onions Make You Cry?
https://www.healthline.com/health/why-do-onions-make-you-cry#takeaway
