[Shaakira Karolia]

Shaakira Karolia  asked the Naked Scientists:
   
Is there a difference between the chemical composition of tears of joy and that of tears of sadness? The little research that I have attempted claims that tears of sadness contain no oxytocin and tears of joy do, but I am unsure as to the scientific validity of this. Your clarification will be most helpful.

What do you think?

[Chemistry4me]

All tears contain 3 chemicals released by the body during stress. They are: 1) leucine-enkephalin -- an endorphine believed to modulate pain sensation 2) ACTH -- a hormone considered to be the body's most reliable indicator of stress and 3) prolactin -- the hormone which regulates milk production in mammals.

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- Emotional tears contain more proteins than ``irritant'' tears, the kind you shed while slicing onions. Though Frey thinks this means that ``something unique happens when people cry emotional tears,'' other scientists have their doubts.

- Both emotional and irritant tears contain 30 times more manganese than is found in blood, suggesting that human tear glands can concentrate and remove substances from the body.

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Scientists distinguish three kinds of tears, which differ from each other by function and also, probably, by composition. Basal tears actually form continuously. We don't experience these minute secretions as tears because they don't "ball up" as we are used to tears doing; instead, every time we blink, our eyelids spread the basal solution out over the surface of our eyeballs. Basal tears keep our eyes lubricated, important in preventing damage by air currents and bits of floating debris.

Basal tears, like all tears, have numerous components. A little bit of mucus allows them to adhere to the eye surface without causing harm. The main part of a tear contains, predictably, water and salts (like sodium chloride and potassium chloride). The ratio of salt to water in tears is typically similar to that of the rest of the body, so there is no net change in salt concentration; nonetheless, if the body's salt concentration climbs too high, it will take advantage of the tear solution and instill it with extra salt. Tears also have antibodies that defend against pathogenic microbes, and enzymes which also contribute to destroying any bacteria the eye encounters. A thin layer of oil covers the tear's outside to discourage it from falling out of the eye before its work has been done.

Our eyes produce irritant tears when hit by wind or sand (or insects or rocks). Irritant, or reflex, tears have the same constituents as basal tears, and work toward the same goal: protecting the eyes. However, since they are designed to break down and eliminate eyeball-intruders like airborne dust, these tears tend to flow in greater amounts and probably contain a greater concentration of antibodies and enzymes that target micro-organisms. Thus, irritant tears are not just basal tears in greater quantity; different biological processes precede the excretion of the two types of solution.

The voluminous tears that so rapidly move us to frustration or pity are, of course, emotional tears. Secreted in moments of intense feeling – sometimes joy, but more often sorrow – these tears aren't there to cleanse the eyes of irritating microbes or debris. Yet they do serve a purpose; the function of emotional tears can be inferred from their constituents. Emotional tears contain much more (maybe 25% more) than basal or irritant tears of a certain important ingredient: proteins.

What do proteins do? Well, what can't they do? We know very well they can be involved in anything and everything. The proteins found in emotional tears are hormones that build up to very high levels when the body withstands emotional stress.

If the chemicals associated with stress did not discharge at all, they would build up to toxic levels that could weaken the body's immune system and other biological processes. But here, as in other areas, the body has its own mechanisms of coping. We secrete stress chemicals when we sweat and when we cry. Clearly, then, it is physically very healthy to cry, regardless of whether or not it feels awkward or embarrassing socially. The reason people will frequently report feeling better after a well-placed cry is doubtless connected to the discharge of stress-related proteins; some of the proteins excreted in tears are even associated with the experience of physical pain, rendering weeping a physiologically pain-reducing process. Conversely, the state of clinical depression – in which many of the body's self-healing processes appear to "shut down," including, often, emotional tears – is most likely exacerbated by the tearless victim's inability to adequately discharge her pent-up stress. Psychologists refer to freely weeping as an important stage in the healing process. But although this notion may appear to be psychological in origin, involving the confrontation of one's own grief, it also just applies physiologically: crying can reduce levels of stress hormones.

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[Don_1]

Fascinating Chem4, thanks for this answer and thanks to Shaakira Karolia for asking. (Not that Shaakira with the eye boggling bum are you? ...sorry, you cannot view external links. To see them, please REGISTER or LOGIN

Does this mean a poke in the eye with a sharp stick isn't such a bad thing afterall?

[Chemistry4me]

I'm sure that Shaakira insn't interested in physiology/scientific debates! Or know anything about it for that matter []

[Shaakira Karolia]

Thank you - all the responses are much appreciated. However, joy and sadness are obviously both emotions and my question concerns whether or not there is a chemical difference between these two categories of emotional tears.