What causes bell's palsy?

Facial Nerve Damage: Bell's palsy is caused by damage to the facial nerve (cranial nerve vii). Frequently the cause is idiopathic and resolves on its own. Other causes can be tumors, lyme disease, HIV infection, sarcoidosis, stroke or multiple sclerosis.

Probably a virus: Bell's palsy is weakness of the facial muscles. It is considered by many to be caused by a viral infection of the facial nerve - although that is not certain. It is important to rule out other causes of facial paralysis such a tumor growth or a stroke before arriving at the diagnosis of bell's palsy. Anyone with facial weakness or paralysis should have a complete medical evaluation by a specialist.