Why Do We Cry? The Science Behind Tears from Emotions to Irritants

Tears often play the role of silent communicators in our lives. Whether it's joy, sorrow, or irritation, tears have a way of expressing emotions when words fail. But have you ever wondered why our eyes well up with tears during moments of extreme happiness or sadness? Let’s dive into the science behind tears and why they flow under different circumstances, from emotional outbursts to cutting onions.

Tears Keep Our Eyes Hydrated

From a scientific perspective, tears are essential for maintaining the health of our eyes. Tears aren't just for expressing emotions; they play a crucial role in keeping our eyes moist and functioning properly. These types of tears, known as basal tears, are constantly produced to lubricate the eyes, keeping them hydrated and protecting them from drying out. While these tears don’t overflow like emotional ones, they silently keep the eyes healthy by maintaining moisture.

How Tears Are Produced

Tears are produced by special glands in our eyes called "lacrimal glands." These glands are responsible for generating tears throughout the day. On average, we produce about half a teaspoon of tears daily, a sufficient amount to keep our eyes moist. Tears consist of water, salt, oils, mucus, and germicidal chemicals that protect the eyes from infection. When we blink, these tears spread evenly across the surface of our eyes, creating a protective shield.

However, when external irritants like dust, smoke, or chemicals from cutting onions get into our eyes, our lacrimal glands jump into action, producing reflex tears to flush out the irritants. These reflex tears are a protective response, triggered by the presence of harmful substances in our eyes.

The Role of Hormones in Tears

Hormones also play a significant role in tear production, especially during emotional moments. When we experience extreme emotions like joy or sadness, stress hormones like cortisol and adrenaline become active. According to psychologist Robert Provine, the part of the brain that processes emotions is the same part that controls laughing and crying. When these hormones flood the system, they trigger an emotional reaction, causing us to cry.

The Science of Emotional Tears

When we cry due to emotional reasons, the brain sends signals directly to the lacrimal glands to produce tears. These tears are not just about physical irritation but are deeply connected to our emotional state. Whether we are overwhelmed by happiness, grief, or even fear, our brain stimulates the tear glands, causing an overflow of tears. In this case, we experience what is known as "emotional tears."

Interestingly, emotional tears differ from reflex tears. They often flow in greater amounts and may even cause a runny nose as they overflow from the eyes and drain through the nasal passages. This shows how deeply connected our emotions and physical responses are, and why some people cry more easily than others depending on their emotional sensitivity.

Why Do We Cry When Cutting Onions?

Cutting onions often causes an uncontrollable flow of tears. But what’s the science behind it? Onions contain sulfur compounds that are released when the layers of the onion are cut. These compounds mix with an enzyme called alliinase, producing a gas called propanethial S-oxide. When this gas reaches our eyes, it mixes with the moisture on the eye’s surface to form a mild acidic substance, which causes irritation.

To protect the eyes, our lacrimal glands produce tears to wash away the irritants, resulting in the teary-eyed experience that many of us are familiar with. Some people reduce this effect by cutting onions under running water or chilling them beforehand to reduce the release of the gas.

Why Smoke Causes Tears

Smoke can also cause a stinging sensation in the eyes, leading to tears. The tiny particles and chemicals in smoke irritate the eyes' sensitive surface, triggering the production of reflex tears to clear out the irritants. Substances like sulfur dioxide, carbon, and nitrogen oxides in smoke can exacerbate this irritation. In polluted environments or when exposed to cigarette smoke or burning materials, our eyes react by tearing up to cleanse and protect the surface from harmful compounds.

Tears: A Defense Mechanism

Tears are an essential defense mechanism for our eyes. They keep the eyes hydrated, flush out harmful substances, and even act as a physical manifestation of our emotional states. While some may see tears as a sign of weakness, they play a vital role in protecting our eyes from dryness and potential damage.

Reports suggest that on average, human eyes produce between 15 to 30 gallons of tears each year. Whether they’re triggered by emotion or physical irritants, tears are crucial for eye health and a fundamental part of how we interact with the world around us.

So, the next time tears well up, remember they are not just an expression of emotion but also nature’s way of keeping your eyes safe and healthy.