Why, in the films, does grima wormtongue sweat? He's constantly wet. A side question is bilbo sweats too at his party just before he 'disappears'? Why?

I had a whole lot of "whys?" while watching those films.Why?
I'd say Bilbo was nervous because he had been pondering what he was going to do and knew it was a huge deal. Grima was just a sleaze.Why, in the films, does grima wormtongue sweat? He's constantly wet. A side question is bilbo sweats too at his party just before he 'disappears'? Why?