Re: Can you 'run out' of tears?

Hi Melanie,
hope all is well with your friend!
Many apologies for taking my time to answer your question. It is a great 
question but, to be honest, not easily answered. Like many areas of 
science, we simply do not know the full answer.
Having said that there have been studies into crying and I will share 
with you what I have found.
When we are emotional and under stress we produce various hormones and 
chemicals which enable our bodies to cope with extreme situations. For 
example, we produce adrenalin when we are about to do something like 
running a race, going for an interview, sitting an exam or running away 
from danger. After the stressful situation has ceased to be an immediate 
threat we have a lot of waste chemicals that have built up in our bodies. 
A quick release valve for these toxic waste chemicals is crying! When we 
cry we get rid of nasty chemicals very quickly and this make us feel 
better. Our brain tells us when its time to stop although our emotions 
can keep things going longer than physically necessary. A good cry really 
does make you feel better!
Crying due to eye irritation (from say onions) is free of these waste 
substances and there have been studies to show this. The tear ducts 
produce various substances to lubricate and clean our eyes. This is a 
continuous process aided by blinking to spread the ‘tears’. Normally 
these fluids are drained to our nose through the tear ducts and are 
hardly noticeable unless you have a cold. 
So back to your question; we produce ‘tears’ all the time but after 
extreme stress or emotion we produce more. So no normal, healthy people 
can’t run out of tears but we can slow the rate of production or speed it 
up, this is a typical biofeedback mechanism. Biologically this removes 
toxic chemicals and therefore makes us feel better. From a more human 
perspective, we are definitely different from most other mammals when it 
comes to crying and our crying behaviour is not, in my opinion, 
convincingly explainable. 
The last major study was about 30 years ago**, so maybe its time to get 
some people crying again!
Next time your friend cries, ask her politely if you can sample her 
tears. I am sure she will want to further the cause for scientific 
knowledge. What do you think?

Take care, and don't cry over spilt milk,

Sean

**Ref: William H. Frey II, Ph.D; Carrie Hoffman-Ahern; Roger A. Johnson, 
MD; David T. Lykken, Ph.D; and V.B. Tuason, MD, on the "Crying Behavior 
in the Human Adult."