I wish I could say whats causing it. If I had to narrow it down to one thing I would say it is from the yellowish stringy saliva. I actually stopped taking the nausea meds because it seemed that they were actually making me tired and dizzy themselves. And when I looked these drugs up, thats what some of the side effects are. So I tried to stay away from them for a while, especially since it seemed that whenever the saliva was present, I was nausious. Maybe my question should be, how do I get rid of the saliva? This is very frustrating