Why Do We Cry? – The Science of Crying


Why do we cry - Geekswipe - Res - 1

Crying is an indigenous attribute of humans and a few other mammals, which is induced by different emotional factors like pain, happiness, sadness and other factors like irritants and dust. Have you ever wondered why do we cry and shed tears?


Tears are not always emotionally triggered. Indeed, you have tears in your eyes now and it will be present in your eyes all the time. These are called as basal tears. They prevent the cornea of the eye from drying by keeping the eye moist and lubricated permanently.

Tear Gland

Tears can also be triggered when your eyes are contaminated with foreign particles that irritate the eye. These reflex tears protect the eyes from the irritants. They are produced by the lacrimal glands, when the brain triggers it.

For example, when you are chopping an onion, the onion vapor – an irritant combination of sulfuric acid, sulfur dioxide and hydrogen sulfide, enters the eyes. The sensory receptors in our cornea, which are extremely sensitive to irritation and pain, signal the brain about this irritation or the presence of the compound. Then the brain sends certain hormones to the lacrimal gland, which in turn produces reflex tears to get rid of the irritant. This process also produces tears when you are exposed to dust particles, smoke and other irritants.

The psychic tears, also called as the emotional tears are triggered by the emotional response of humans. While there is a dispute that humans are the only living organisms to cry emotionally, we can ignore that for now and delve into the mechanism of human emotional tears.

When a person feels sad, the stress from the emotion produces high levels of stress hormones and toxins in our body. This is sensed by the hypothalamus. This endocrine gland besides with the other glands secretes hormones that trigger the lacrimal gland to produce tears. This mechanism helps the body to get rid of the excess hormones and toxins with the help of tears. Obviously, the emotional tear content has more proteins, stress hormones and endorphins. The major protein present in the emotional tears is the prolactin – a protein that controls breast milk production. And hence, this might be the reason why females tend to cry often as the levels of prolactin is higher in their system when compared to the males.

In a different context, we can comprehend that the emotional tears might be produced as a psychological response when we are down in the dumps. As humans, we are dependent on the fellow beings for emotional support. And it turns out that tears are the only way to express the emotions to other human beings. You can always find this in toddlers, as sometimes they cry solely to manipulate their parents in to buying them an awesome toy.

Crying is good

So, crying does helps us to cope up with grief and share the joy as well. Researchers have also confirmed that people do feel better after they cry, as they get rid of the stress hormones via tears.

When you feel sad the next time, don’t control your tears. Let it flow down your cheeks for a while. You will feel better or for the least, you’ll have a shoulder by your side to soothe you.

Image: Kamaljith | CC BY

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This post was first published on May 25, 2014.


Karthikeyan KC

Aeronautical engineer, dev, science fiction author, gamer, and an explorer. I am the creator of Geekswipe. I love writing about physics, aerospace, astronomy, and python. I created Swyde. Currently working on Arclind Mindspace.

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2 Responses

  1. I usually cry if my fridge is empty. lol!! I never knew that onions are so evil. Good article!