via AAO

One of the many mysteries of our daily life is why onions make us cry. The majority of meals have onions on them, no matter in what region of the planet you are, this will be a common thing in kitchens, and everybody will have the same irritating issue.

This is very annoying, no one wants tears in their food, and sometimes it is so strong that we have to rest for a bit until tears go away. So, what is it about this weird edible that makes our eyes fill with tears for no apparent reason? Today we are going to solve that question.

Like everything in the world, this has a scientific explanation. Onions are not only full of leaves but also have a lot of water and natural chemical substances inside them. Scientifically speaking, this is the result of various biochemical reactions that happen between the components of the onion and our enzymes that triggers a tear factor that stimulates our sensitive optic nerves and eye blood vessels.


So, Why Do Onions Make Us Cry?

via The Conversation

It all comes down to those chemical solutions that are released into the air when the onion is cut. Most of the compounds have sulfur on them, which evaporates while we are cutting the vegetable and the gas gets into our eyes.

This sulfur-full gas irritates the eyes and crying only makes it worse. When it is mixed with the water of the tears, it creates sulfuric acid which causes itch and more irritation, while our blood vessels dilate and make our eyes red.

As a defense response, the brain makes us tear more to dilute the acid and protect our eyes, but it ends up being a never-ending cycle until we are no longer in touch with the previous gas.

Funny enough, onions produce this tear gas to avoid wild animals from eating them. Basically, this is their defensive method. The gas will affect all creatures the same way, but us humans are able to ignore it and just go along to introduce them into our food.

Now, there are some ways to prevent this reaction. Some people like to use glasses to protect their eyes, while others simply put them in the freezer since the cold will decrease the function of the proceeding gas, directly cutting the onion underwater so the gas will react with other water than the one contained in our eyes or using a thin and really sharp knife to avoid the breakthrough of the cells that the onion contains so the production of the gas is less.