Bell's palsy is an unexplained weakness or paralysis of the muscles on one side of the face that affects approximately 40,000-65,000 Americans each year. People with Bell's palsy may be unable to close the eye on the affected side, and may also experience tearing, drooling, and hypersensitive hearing. Bell's palsy can begin quite suddenly, sometimes appearing overnight. Although this disorder is unsettling and inconvenient, it is typically not indicative of a serious health problem. The weakness and paralysis eventually disappear in the majority of cases.

Facial palsies have been linked to conditions such as Lyme disease, ear infection, meningitis, syphilis, German measles (rubella), mumps, chickenpox, and infection with Epstein-Barr virus (e.g., infectious mononucleosis). Bell's palsy is diagnosed when these other conditions have been eliminated.

The root cause of Bell's palsy has not been identified. Although Bell's palsy is not life-threatening, it can present symptoms similar...