The Lachrymatory Factor Makes You Cry Every Time You Cut Onions

Fareeha Arshad
Photo by Mockup Graphics on Unsplash

Let’s admit it: our meals are incomplete without onions. Our taste buds will immediately notice the missing caramelized onions in our burgers, the lack of onion rings on the plate, or no onions in the onion soup. On average, 93% of American restaurants use onions in some of their top-selling dishes, and an average American consumes about twenty pounds of onion every year.

Despite their high demand, enjoying onions comes with a heavy price: Who else hates the tears that starts flowing the moment your knife touches the onion?

The primary reason behind excessive tearing is a chemical, lachrymatory factor that irritates the eyes. The moment you start peeling or cutting onions, a group of chemicals called alliinase and cysteine sulfoxides mix and result in their reaction forming sulfenic acid. This sulfenic acid follows either of the two paths. It undergoes rapid condensation to form an organosulfur compound that gives onions their pungent smell and strong flavour. Or else, the sulfenic acid gets transformed into the lachrymatory factor.

According to researchers, this factor is directly linked to the flavour of the onions. That means, more the lachrymatory factor is produced, the more is the flavour of the onions. When we cut onions, this lachrymatory factor is formed and is volatile. It quickly evaporates from liquid form to vapour form that irritates and, consequently, tearing when it reaches the eyes. The lachrymatory factor is naturally produced to protect the onion plants from harmful insects and animals.

To protect your eyes from irritation, you can always use a face shield or a sharper knife that is known to trigger lesser production of the lachrymatory factor. Also, you can always soak the onions in water for ten minutes before you cut them. It limits the amount of the factor produced and thus reduces the irritation of the eyes.

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I am a scientist by profession and a historian by passion. I write about current affairs, history, science, and lifestyle.

Texas State

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