I just joined when I saw this thread--i know it's been a month, but i'm hoping you're still checking this one!
I'm no doctor, and i'm no ent expert, but I have read about this before. Have your friend test the texture of this substance by letting some drip onto a white paper napkin. If the napkin dries, and there is no evidence anything was on it (just like if it had only been water), he needs to go to the doctor right away!!! (if he hasn't already, since it's been awhile.)
not saying it is serious, but there is a serious condition with these symptoms, and he'll want to rule it out right away. I forget the exact name, but it involves the leakage of cerebro-spinal fluid. The stuff is water-like, tasteless (i believe), and usually it doesn't stop on its own. I'm not sure if there are any other symptoms like dizziness.
Don't mean to scare, like I said--i've only read about this and thought you should know so your friend can get it checked out!