Eli5: how come tears don’t sting our eyes even though they are salty?
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Salt stings because of osmotic pressure. Water moves out of your eye cells to balance the salt concentrations inside/outside.
Tears have the same concentration of salt as the inside of your cells so that does not happen. It’s also why lubricating eye drops containing saline don’t sting either.
Salt stings because of osmotic pressure. Water moves out of your eye cells to balance the salt concentrations inside/outside.
Tears have the same concentration of salt as the inside of your cells so that does not happen. It’s also why lubricating eye drops containing saline don’t sting either.
All of your insides are salty. All living things are basically complicated bags of slightly salty water. Your tears are no more salty than the water inside your cells, or your blood. But they do *taste* salty, so why is that? Well, your tongue is good at detecting salt, and tears *are* more salty than fresh water. Also, tears are pretty much just water and salt, unlike blood, for instance, which also has a lot of iron which gives it its distinctive flavor. You (probably) don’t think of blood as salty because that’s not its dominant flavor.
So the reason tears don’t sting your eyes is that they are exactly as salty as your eyeballs, and exactly as salty as your eyes prefer to be. Which is salty enough to taste, but nowhere near as salty as, say, sea water.
All of your insides are salty. All living things are basically complicated bags of slightly salty water. Your tears are no more salty than the water inside your cells, or your blood. But they do *taste* salty, so why is that? Well, your tongue is good at detecting salt, and tears *are* more salty than fresh water. Also, tears are pretty much just water and salt, unlike blood, for instance, which also has a lot of iron which gives it its distinctive flavor. You (probably) don’t think of blood as salty because that’s not its dominant flavor.
So the reason tears don’t sting your eyes is that they are exactly as salty as your eyeballs, and exactly as salty as your eyes prefer to be. Which is salty enough to taste, but nowhere near as salty as, say, sea water.
All of your insides are salty. All living things are basically complicated bags of slightly salty water. Your tears are no more salty than the water inside your cells, or your blood. But they do *taste* salty, so why is that? Well, your tongue is good at detecting salt, and tears *are* more salty than fresh water. Also, tears are pretty much just water and salt, unlike blood, for instance, which also has a lot of iron which gives it its distinctive flavor. You (probably) don’t think of blood as salty because that’s not its dominant flavor.
So the reason tears don’t sting your eyes is that they are exactly as salty as your eyeballs, and exactly as salty as your eyes prefer to be. Which is salty enough to taste, but nowhere near as salty as, say, sea water.
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