At night my mouth gets so dry my tongue hurts in the morning. harmful?

What's the cause?: It's not healty, but i'm more concerned about why your mouth gets so dry. Are you taking any medications that might cause it? Do you have a sinus infection causing you to 'mouth breath' at night? Is it simply a very warm, dry room (get one of the cold steam humidifiers and run it by your bed at night...).

Dry mouth: If your mouth is extremely dry only on awakening in the morning, you probably sleep with your mouth quite open. Is your nose clogged? Do you sleep on your back all night? Do you need a humidifier in your bedroom during the winter? Unless you have sleep apnea there is no harm with am dry mouth.