Why do humans leak from eyes and nose when sad?


Why do we cry, and why does our nose run when we are sad? What’s the explanation behind it?

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Your nose runs because tears don’t just leak out your eyes, they also drain through your nose. And these tears can mix with mucous and then you get gross snotty discharge when you cry.

As for why we cry at all, it’s sort of difficult to know for certain what evolutionary goal was being achieved when the earliest humans started to cry. But shedding emotional tears triggers a cascade of hormones that can improve your mood and relieve stress.

There’s also a theory that their function is to alert friends and family that we’re upset. The logic behind this is that humans are an incredibly social species and in the earliest humans this was their most valuable asset. We didn’t have claws, or massive jaws with teeth or venom. We could throw things and we lived in cohesive families where teamwork was essential. So crying might have been a way to signal to provoke support or help.

Firstly, emotional tears are *not* the same as irritation tears chemically. In theory if you sampled a tear drop you would see different chemicals in it and would be know if it’s because the person is sad, or because the person has sand in their eye.

Secondly, emotional tears achieve two things. We know that releasing emotional tears is directly related to the production of various brain-chemicals and feelings of relief and pleasure. This is why “having a good cry” is a thing. Crying emotionally actually makes you happier. Secondly, humans evolved as a social species before we had language, and our faces are a primary source of knowledge of our peers. *You* don’t just cry, but *other people* see you cry and learn from that. They learn you’re upset, you’re in a mood and their knowing this, somehow, proved beneficial to our survival as a species. Hence, the trait was passed along.

When we cry, our eyes produce tears as a response to an emotional trigger. The tears contain hormones and proteins that are released in response to the emotional stimulus. The tears also contain an enzyme that helps break down the proteins and hormones in the tears. The tears then travel down the tear ducts and into the nose, where they mix with mucus. This mucus is then secreted from the nose, resulting in a runny nose.