Why do saliva drips when we sleep?

When your mouth opens your on salivation glands secrete saliva which has enzymes that are used to break down your food for digestion. When your mouth opens these glands don't know if you are eating or not, they just do their job. Likely when you fall asleep your face muscles relax, and your mouth comes open producing the saliva which falls out of your mouth when you sleep. A large amount of saliva might be a sign that you talk in your sleep, since the movement of the jaw produces it at a larger rate.

Gee, I hate that. I am thankful to God that this doesn't happen to me. It was happening when I was young. Now, I don't have that problem. Do you have?

Hey, that's simple - it's invisible ink to draw the world map on your pillow to strategize of conquering the world or even chart where your next travelling destinations while you're dreaming in your sleep. Through time, you'll notice the world map materialize on your pillow when you're changing your pillow case, hahaha

well if your mouth is open and your head is down it's gravity going thru an opening.

Lol, yes its not a very attractive site when this happens. It probably happens when we leave our mouths open whilst we are sleeping, and our head is faced down...

LOL, this happens to me all the time, it happens because I sleep with my mouths often (that is also the reason why do I often get sore throat). Hate when I wet my pillow...