Photo Creative Commons License by landeth
I've been think a lot lately about tears, and have shed quite a few. I have been working on my family genealogy hard and heavy, and I finally found some data for a missing family. It turns out the oldest son went off to fight in the Civil War at age 17. He was furloughed about a year later and came home to the joy of his parents and his 9 brothers and sisters. The joy soon turned to ultimate sadness, as he had been exposed to Diphtheria. Within 3 weeks of his return home, he and 8 of the other 9 children were dead. I cannot begin to imagine what that mother felt, nor the tears she shed.
Our several kinds of tears are chemically different, depending on why we shed them. Some tears are protective; they keep the eye lubricated and help wash the eye of debris. Those are called basal tears and are mainly water and salt, but they also contain antibodies that defend against pathogenic microbes, and enzymes that destroy foreign bacteria. The biggest difference in basal tears and protective tears is usually in the amount of them. For example, it takes far more tears to wash away airborne dust, or sand in a windstorm, than to keep the eye moistened in normal circumstances.
The tears produced by slicing onions is the body's attempt to wash the eyeball of strong irritants. The fumes given off by the onions contain sulfenic acids. You can peel an onion under running water to avoid most of the fumes, but a trick that works when chopping onions by hand is to hold a slice of bread in your mouth. Sure, you'll look goofy, but it will prevent the irritants from reaching your eyeballs!
Sad, emotional tears are another matter altogether. They are the body's way of discharging toxins built up by negative emotions. Those tears contain lots of hormonal proteins, and 30 times as much manganese as blood serum. Autopsies of severely depressed people reveal unusually high concentrations of manganese in the brain tissue. Thus it seems that crying releases some of that excess manganese, preventing other biological complications.
Emotional tears also contain mood-elevating and pain-reducing endorphines, which explains why we feel better after a good cry. Crying is the most inexpensive, natural and powerful mechanism we have for coping with pain, stress and sorrow. Happy tears are mostly just the body's normal saline solution.
So, cry as much as you want to; it's probably good for you. But no cheating by cutting onions... your tear ducts know the difference!