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Sometime ago I'd heard someone trained in child psychology claim that crying for emotional reasons (as opposed to getting something in your eye for example) released toxins from the brain and/or body. More specifically, she claimed that emotionally-based tears, when collected and fed to rats in their food, resulted in a markedly increased statistical rate of disease and mortality in comparison to reflex-based tears or no tears at all. The explanation seemed a little hand-wavy, was uncited, and I was a little bit suspicious.

However, I have noticed for some time that emotionally-based tears taste different depending on the "bitterness" of the experience. Then, I recently went through an extremely stressful time where I experienced levels of emotional stress higher than I ever have in my life. I found to my surprise that my tears during this period, if allowed to drain down my throat, caused extreme soreness for a short period of time (mitigated by drinking liquids); whereas if I was careful not to allow them to, no soreness resulted. A friend also experiencing extreme emotional stress found that the specific areas on her cheeks that her tears touched became visibly red and raw. Again, her experience was that the rawness correlated with contact vs no contact in specific incidents--rather than frequency. These responses seemed too specific to be psychosomatic.

Now, "toxins" is very vague and it's clear that crying is an important emotional tool regardless of whether its significance is psychologically- or physiologically-based. My sample-space is unsatisfactorily small, but has intrigued me. Is there any scientific evidence that:

  1. Emotionally-driven tears contain substances harmful to the body, and if so which substances and by which mechanisms.
  2. Emotionally-driven tears contain substances which are in some way specifically related to stress.
  3. And, if either of the above are true, is it scientifically plausible that the substances in emotionally-driven tears are in any way originating in the brain?

I'm especially interested any evidence which suggests there is a good reason to fully expel emotionally-driven tears from the body, and any that suggests failure to cry under emotional stress prevents the release of a substance which ought to be released for body/brain health. Does anyone have any good research on these topics? My apologies for the length and detail of the question.

Edit: I've also recently experienced stinging cheeks after an especially poignant (yet low tear volume) cry. Since this is now a topic of curiousity for me it's hard to rule out a psychosomatic effect, but it was a distinct enough feeling to bump this post with an edit. No hard sources out there, anyone?

  • Another anecdote: I wore soft contact lenses when I had a nephew die of SIDS. My contacts almost immediately started to feel rubbery, and badly needed enzymatic cleaning. Obviously, I was getting something into my eyes that wasn't normally there. What this was (aside from having some protein), or how harmful it was, I couldn't tell. – David Thornley Apr 28 '11 at 3:37
  • Yes, anecdotal evidence seems to abound on this one. But I'm hoping someone here might have some hard science for us! – eMansipater May 3 '11 at 18:15
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    What are "toxins"? I've been under the belief, right or wrong, that anything that says it will "release your toxins" is hogwash. – SteveGSD Jun 22 '11 at 0:57
  • @CowKing It's an unsatisfactorily vague term for sure. The term unfortunately gets used as a catch-all for "substance with harmful effects for a biological organism" rather than the more specific "biologically-produced poison" the term technically refers to. – eMansipater Jun 30 '11 at 16:58
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    Are there more/different toxins in tears of negative emotions (anger, sorrow, grief, heartbreak) than tears of positive emotions (joy, happiness, relief, self-pride, accomplishment)? – user14662 Jul 21 '13 at 20:17
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There does seem to be a distinct difference in composition of emotional tears, compared to basal and reflex tears (review in german). The emotional tears were found to contain about 24% more protein than reflex tears (Frey et al., 1981). Also found were increased concentrations of Prolactin, manganese, potassium compared to serum concentrations, as well as increased serotonin concentrations compared to reflex tears.

This research shows that emotional tears are different from reflex tears, but it doesn't really support the claim that toxins are eliminated through crying. The german review I linked states that it is unlikely that toxin elimination through tears has a therapeutic effect. One additional aspect arguing against that is the fact that a large part of the tears is usually reabsorbed through the skin.

This does not mean that there are no psychological or social effects of crying. But I could not find any evidence for specific toxins that are excreted via tears, the substances in the research I mentioned are not really toxins.

  • "the substances in the research I mentioned are not really toxins." - I wonder if there's some separate research on effect of those on the facial tissues – user5341 May 13 '11 at 15:53
  • I'd have the devil of a time finding the reference... But years ago in the the old pop-science magazine OMNI they had an article on this very thing, that crying could be considered an "excretory" process in some cases, removing a buildup of certain hormones.... – M. Werner May 13 '11 at 16:03
  • Actually manganese has a small genotoxicity and is neurotoxic in large amounts, but I don't think crying is an efficient way to get rid of toxins... :D – inf3rno Oct 18 '14 at 1:36
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Yes, emotional tears help you excrete stress hormones from your body. As others have said, "toxins" is probably nonsense.

Emotional tears have special health benefits. Biochemist and “tear expert” Dr. William Frey at the Ramsey Medical Center in Minneapolis discovered that reflex tears are 98% water, whereas emotional tears also contain stress hormones which get excreted from the body through crying. After studying the composition of tears, Dr. Frey found that emotional tears shed these hormones and other toxins which accumulate during stress. Additional studies also suggest that crying stimulates the production of endorphins, our body’s natural pain killer and “feel-good” hormones.” Interestingly, humans are the only creatures known to shed emotional tears, though it’s possible that that elephants and gorillas do too. Other mammals and also salt-water crocodiles produce reflex tears which are protective and lubricating.

Prolactin is the stress hormone (as mentioned in Mad Scientist's answer).

There is some question as to whether crying is always beneficial for all people, though.

In a study published in the December issue of The Journal of Social and Clinical Psychology, Dr. Rottenberg, along with Lauren M. Bylsma of the University of South Florida and Ad Vingerhoets of Tilburg University in the Netherlands, asked 5,096 people in 35 countries to detail the circumstances of their most recent crying episode. About 70 percent said that others’ reactions to their breakdown were positive, comforting. But about 16 percent cited nasty or angry reactions that, no surprise, generally made them feel worse.

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