Emotional, Irritated, Faking It—Why Do Humans Cry?

You hear some bad news, your friend tells you a really good joke, or you enter a smoky room. All of these events might leave you crying, but all tears are not created equal. The tears our eyes produce actually vary in composition depending on the occasion. 

Let’s dig into how our eyes produce tears, the kinds of tears our eyes produce, and why we cry at all.

How are tears made? 

Healthy eyes have small organs called lacrimal glands that sit right above the eye and secrete tears when triggered. When tears are produced, blinking then moves them across the surface of the eye before they're carried away by our tear ducts.

Those tear ducts (also called nasolacrimal ducts) drain into our nose. So when you cry a lot, the tears mix with the mucus in your nose. And if you cry even harder, not all those tears can fit in the drainage system. Instead, they fall out onto your face to make you a snotty, teary mess. Fun!

Since newborn babies don’t yet have fully developed lacrimal glands, they can cry without actually producing any tears.

According to the American Academy of Ophthalmology, we make 15-30 gallons of tears each year. That may sound like a lot, but don’t worry, you won’t run out. 

Different kinds of tears

Our eyes make three kinds of tears, each with their own composition or biochemistry.

Basal tears

First up, we make around half a teaspoon each day of something called basal tears. These are the tears responsible for lubricating our eyes so they don’t dry out. Basal tears have three layers:

• An inner mucus layer that keeps them attached to your eye
• An aqueous layer that protects your cornea (and also has some germ-fighting enzymes)
• An oily outer layer that keeps the surface of your eye smooth

Our eyes naturally get drier as we age, and there is a test called the Schirmer test to check that your eyes are producing enough basal tears. In the Schirmer test, if you place a piece of paper at your lower eyelid, 15 millimeters of the paper should be wet after five minutes. Certain activities can increase dry eye, like staring at a computer screen for long periods of time.

Reflex tears

Your eye produces reflex tears in response to an irritant. Ever find yourself crying as you chop...

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