If you check parasite symptoms you'll find out it's caused by parasites.
I've had heavy drooling while asleep for years until last year (I always thought it was due to sleeping very deep). I was getting ready for the liver cleanse and started a parasite cleanse even though I knew I didn't have parasites.
It wasn't until a couple of months ago that I was checking out the parasite symptoms and saw heavy drooling as a symptom and I realized I wasn't drooling anymore.
Waaaay cool.
I used the Clarkia tinture.
Good luck.
As a side note (if I remember correctly) I've read where Andreas (SP?) belives this is caused by lack of salt (sea) as well (or something like that). So if the parasite cleanse doesn't work check into that.