Travelers who use a scopolamine patch behind the ear to prevent motion sickness are usually all too aware of the oral dryness this drug causes.

Oral dryness may also be caused by mouth breathing, usually caused by partial obstruction of the upper respiratory tract.

Xerostomia is the subjective feeling of oral dryness, which is often (but not always) associated with hypofunction of the salivary glands.

Specialists say its major strength is that it stays active on the teeth for hours, but side effects can include a bad taste in the mouth, oral dryness or burning, and temporary tooth discoloration.