One of the most common causes of dry mouth at night is breathing through the mouth instead of the nose. When air passes through the mouth for hours, it dries out saliva and leaves the mouth feeling sticky or dry by morning.
Mouth breathing may happen because of nasal congestion, allergies, a blocked nose, a deviated septum, sleeping position, or simple habit. The source article also lists nasal congestion, mouth-breathing habits, and sleeping position as common reasons mouth breathing can lead to nighttime dryness.
If you often wake up with a dry mouth, ask yourself: do you snore, wake with a dry throat, or breathe through your mouth when your nose is blocked? If yes, improving nasal airflow may help.
2. Dehydration
