Re: How come your eyes water and your mouth waters but not your ears or nose?

Good question Jeanine!

You probably notice that your eyes water when you get something in them-like 
an eyelash or a speck of dirt.  Tears are our bodies' way of getting rid of 
this foreign object in our eye before it can scratch or otherwise harm the 
surface of the eye.

But if you think about it, our  nose and ears do the same thing.  When we 
sneeze (or at least when I sneeze), we get a runny nose afterwards.  This is 
another way for our body to get rid of dust or pepper or whatever is 
bothering our noses out of our bodies.  Both the sneezing part and the runny 
nose part are important in this process.

Ears don't water exactly, but they do make wax.  And this wax helps keep out 
dirt and water and other things that could clog our ear canal. 

So what you've seen here for eyes, nose and ears, is that watering (or wax) 
are important to get bad things out of our bodies, or to protect our bodies 
from these bad things in the first place.


The question about our mouths watering is a little different.  When our 
mouths water, it's usually in response to smelling or seeing something good 
to eat (for me it's definitely chocolate chip cookies).  The "water" is 
actually saliva.  And saliva plays an important role in digestion.  First it 
helps keep the food moist while chewing.  And secondly it contains enzymes 
which start the digestion process, even before the food gets to our 
stomachs.  We call this mouth watering phenomenon 'conditioning'  which is 
just a fancy way to say that if we see food it probably means we will be 
able to eat that food soon and our body is just getting ready to digest it.

Hope this is helpful!  Please let me know if you want more information on 
any of these subjects.

-Sarah Tegen
tegen@alum.mit.edu