Cutting Onions Can Make People Cry, But Why?

It is common knowledge that people could shed some tears when cutting onions, but why exactly do onions make people cry?

Why Cutting Onions Can Make People Cry

Onions are bulbs that mature in the soil. The subterranean home of these bulbs is inhabited by different creatures, such as voles that love nibbling on bulbs, tubers, and roots.

To prevent this from happening, onions have a defensive mechanism that is meant to protect them against hungry predators. They release sulfenic acid and enzymes when their skin breaks. Such compounds mix to produce an irritating gas known as propanethial S-oxide.

This gas is a lachrymatory agent, which means that it causes tears when it gets into contact with the eye. Propanethial S-oxide also becomes sulfuric acid when it touches the layer of water that protects and covers the eyeballs.

However, similar to onions, the eyes also have a defense mechanism designed for protection against harm. When nerves in the eyes pick up a lachrymatory agent, they produce tears for these to be flushed out.

There are also some individuals who are more likely to cry when cutting onions. Individuals who are allergic or sensitive to onions and other kinds of alliums may have more severe reactions. They may experience symptoms like tingling, itching, or hives.

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Onion Type Matters

Some onion types can also produce more or fewer tears. Onions that have the strongest chemical reactions are those with lots of compounds that contain sulfur. These types include white, red, and yellow onions.

The sweeter onions, such as green onions, contain less sulfuric content. They are also less pungent and produce fewer tears.

With genetic modification, crop scientists were also able to make tear-free varieties of onions. Though these varieties are not yet mass-produced, they can be found as Sunions across some specialty markets.

Home Remedies For Onion Tears

Though they may sting, onion tears do not pose any danger to the eyes. They are just annoying.

Nevertheless, to reduce discomfort and redness, people may want to treat their burning and irritating eyes immediately. Some remedies to reduce tears due to onion irritation include keeping a distance from the onion being cut, rinsing the eyes with clean and cool water, using lubricating eye drops, placing cool cucumbers or cold compress over the eyes, and using other remedies for sore eyes.

Dr. Abby Thiel, a food scientist and host of the "Abbey the Food Scientist" YouTube channel, also shares that using a fan, protecting the eyes with goggles, chilling the onion, turning up the heat, lighting candles, or adding acids could help combat onion tears.

Crying while cutting onions could also be prevented by cutting the bulbs properly, using water, and protecting oneself against vapors.