DROOLING problem help!?

For the past two nights I have woken to to a really unpleasant sensation of my boyfriends cold drool running down my arm. It happened once and I thought that it was a one time thing. Next night it happened again. It is really sudden because he has never drooled before and I hated to touch my arm to see what was tickleing me and waking me up to feel slimy slobber. Sick! I woke him up and showed it to him. I know that he cant help it but he should see how horrible it is. the only thing that he has done differently is that he drank Red Bull on those two days but surely that isn't making him slobber. I feel bad but if it happens again i'm gonna wipe it on him and is there something wrong with him?