Why Do We Cry? The Science Behind Our Tears
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Why Do We Cry? The Science Behind Our Tears

Explore the science of tears, including why we cry, the different types of tears (basal, reflex, and emotional), and their unique functions and benefits for eye health and emotional well-being.

Published February 16, 2024

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Have you ever found yourself tearing up during a heart-wrenching movie or while cutting onions and wondered why our bodies react this way?

It turns out, the act of crying is far more complex and beneficial than many of us realize.

Each year, our eyes produce an astonishing 15 to 30 gallons of tears, serving various essential functions beyond merely expressing sadness.

Let's dive into the fascinating world of tears, their types, and the science behind why we cry.

The Unique Nature of Human Tears

While many animals can shed tears, humans are thought to be unique in their ability to cry emotional tears.

A recent study from Japan did, however, discover that dogs might shed tears of joy when reunited with their owners, suggesting there's still much to learn about this phenomenon.

But what exactly triggers our tears, and why do they happen?

Understanding the Types of Tears

Our eyes can produce tears for several reasons, from physical irritants to emotional responses.

These tears are not all created equal; they differ in composition and purpose.

Here's a closer look at the three types of tears:

Basal Tears

Basal tears are with us all day, every day. They form a protective film over our eyes, improving vision and focus while washing away dirt and germs. This continuous lubrication is crucial for keeping our eyes healthy and free from infection.

Reflex Tears

Ever wonder why you start to cry when chopping onions? That's where reflex tears come in. Produced in response to irritants like onion fumes or smoke, these tears help wash away harmful substances. Rich in water and containing antibodies, reflex tears play a key role in defending our eyes from external threats.

Emotional Tears

Perhaps the most intriguing of all, emotional tears are triggered by intense feelings, whether of joy, sadness, or frustration. Unlike basal or reflex tears, emotional tears are loaded with additional proteins and hormones, including stress hormones, suggesting they play a role in helping us calm down after a stressful or emotionally charged event.

The Production and Purpose of Tears

Tears are produced by the lacrimal glands located above our eyes, with the mucus and oil components coming from the meibomian glands at the edge of our eyelids.

For tears to function correctly, they need a combination of these substances.

As we blink, tears spread across our cornea, draining into tear ducts and eventually down through our nose, where they evaporate or are reabsorbed.

This intricate system not only keeps our eyes moist and healthy but also plays a crucial role in emotional expression and relief.

Emotional tears, for instance, are believed to have evolved as a way to signal distress or need for support, garnering empathy and social assistance from those around us.

The Evolutionary Purpose of Emotional Tears

Crying emotional tears might serve an evolutionary purpose by fostering social bonds and eliciting support from others.

Research suggests that individuals who receive social support during emotional tearful episodes often feel better than those who suppress their tears or lack a supportive network.


Tears, it turns out, are far more than just saltwater; they're a complex expression of our human experience, serving multiple purposes from eye health to emotional communication.

So next time you find yourself tearing up, remember that these droplets are a testament to our incredible biological and emotional complexity, offering insights into the depths of human emotion and the sophisticated mechanisms our bodies use to navigate the world.