Hi there... age...loss of teeth... I'm guessing here.. I have that problem as well and don't know why.?? maybe I'll ask my dentist..
my roommate has that problem, hers seems to be from sinus issues and sleep apnea; her mouth is opened most of the night, so it seems that a lot of drool leaks out. Could be connected with the sinus issues, like improper drainage, in her case.
Do you snore, or find that your throat is dry when you wake up? Sleep on your side? I suppose it could be something like sleeping with your mouth opened. Just guessing.
I have a buckwheat husk pillow, since I used to sweat a lot at night and my pillow would get wet. I was told that the buckwheat husk wicks the moisture away from your skin, and doesn't get mildewed. It's been great for my neck; I even pack it in my suitcase when I travel. Way more info than you needed, sorry. :o)
you could ask your doctor, if its bothering you. My roommate has gotten some rash in the corners of her mouth from all that drool. I hope she never reads this forum, ha ha!