The Interesting Salty Science of Tears

We know what tears are, but do we know what tears really are? That sounds like a really stupid sentence, but how many of you can say you know what’s in your tears? They’re these salty droplets that come from your eyes when you’re sad, happy, or chopping onions. Why are they even salty? Let's explore what tears are made of and why they taste like the ocean.

The Basics: What Are Tears?

Tears are more than just water coming from our eyes. They're a complex mixture of water, oils, proteins, and electrolytes. Past the chemical makeup, these tears help us release the stresses from our body to function normally everyday. Each tear is like a tiny ocean, both physically and emotionally. They carry important substances to keep both our eyes and hearts healthy and functioning.

Breaking down the tears, they contain:

• Mostly water (about 98%)
• Salts (mostly sodium chloride - the same as table salt!)
• Proteins (like lysozyme, we’ll get more into this later)
• Oils (to prevent tears from evaporating too quickly)
• Mucus (helps tears spread evenly across the eye)
  

The Chemical Structure of Tears

As we know, the basic chemical formula for tears is H2O - just like water. However, all the things we mentioned right above are not accounted for in that formula.

The salt in tears is mostly sodium chloride (NaCl), the same as table salt. There's also potassium (K), calcium (Ca), and magnesium (Mg). These are all electrolytes, which help us maintain a delicate balance of fluids. Without them, our eyes would dry out or become easily irritated, as opposed to being moist and comfortable. They help tears spread out evenly as well. Do you ever notice that when you only have a few tears come out, instead of when you’re in a full out sob, the tears start to well up in your eyes instead of leaking right out?

The electrolyte composition is also important to mimic other bodily fluids. This helps make sure our tears are compatible with our eye tissues, preventing irritation. Even more, these electrolytes are antiseptic/antibacterial, fighting off bacteria from staying on the surface of our eyes.

Other than the electrolytes, proteins like lysozyme and lactoferrin are found within tears. These proteins are the main contributor to fighting off the bacteria and helping our eyes heal, and they wouldn’t be able to exist without having the right electrolyte environment. 

So the next time you feel tears about to come, don’t hold it back anymore. It’s much better for you to cry, think about it as a natural cycle that happens to help maintain your eye health. 

What's Inside Tears?

This is where all those confusing names come in, but it’s still cool to think about!

• Lysozyme: This enzyme can destroy bacterial cell walls, acting as a natural antibiotic.
• Lactoferrin: Another antibacterial protein that also helps with iron absorption.
• Lipocalin: This protein binds to fatty molecules and helps spread tears evenly across the eye surface.
• Immunoglobulins: These are antibodies that help fight off infections.
• Glucose: Yes, there's a tiny bit of sugar in your tears!
• Growth factors: These help in healing and maintaining the cornea.

I don’t expect anyone to remember all this, but it's still interesting, right?

A study published in the American Journal of Ophthalmology found over 1,500 proteins in human tears. That's a lot of complexity in each little drop!

Types of Tears

Not all tears are created equal. There are actually three main types:

1. Basal tears: These are the everyday tears that keep our eyes lubricated. They're constantly being produced and are crucial for eye health. Think about when your eyes are dry. That probably means that your body isn’t manufacturing enough tears! These should always be in your eyes. Tears aren’t only limited to when you blink or are sad when tears come out, they’re constantly there.
2. Reflex tears: These are the tears that flow when something irritates your eye, like dust, wind, or onion vapors. Say you walked past a construction site and some dirt blew into your eye. Your body creates these reflex tears to flush them out. Useful, right?
3. Emotional tears: These are the tears we typically think of - the ones that come with strong emotions, whether happy or sad. This might be your last breakup, a failed test, or just the stresses of life that we all unfortunately have to go through. Cry a little!

With all these different types of tears, the chemical composition actually varies a tiny bit between each type. Interestingly, the American Academy of Ophthalmology actually notes that emotional tears have a different chemical composition compared to reflex tears.
“Higher levels of prolactin, adrenocorticotropic hormone, Leu-enkephalin, potassium and manganese have all been located in emotional tears.”

Why Are Tears Salty?

Now, think about the last time you cried. Maybe it was just a small droplet that rolled down your face and it eventually hit your lips. Wasn’t it a bit salty? Our tears have almost the same salt concentration as our blood plasma. We mentioned that there’s sodium chloride in our tears and this saltiness serves several purposes:

• It helps maintain the right osmotic balance in our eyes.
• The salt acts as a mild antiseptic.
• It helps our tears spread evenly across our eyes.

The concentration of salt in our tears is about roughly 0.9%. Taking seawater into comparison, seawater is at 3.5%. Freshwater, on the other hand, is anything that’s usually less than 1%. Our tears are not quite as salty as seawater, but it could be classified as freshwater, which is not completely salt-free, but definitely still has a decent amount of salt.

Tears are quite interesting and have a lot more depth than just this liquid which comes out from your eyes when you’re sad. Next time you’re sad and feel like crying, maybe you can be amazed instead from how your body reacts as it’s trying to get that sadness to leave your body.

They clean our eyes, fight off bacteria, and even help us process emotions. So don't hold back those tears - they're little marvels of nature, each and every one. You're not just crying - you're taking care of your eyes and processing your emotions all at once. 

It’s okay to cry. These tears are a sign that you're alive, you're feeling, and you're human. And that's a beautiful thing.