Causes

Although the exact reason Bell's palsy occurs isn't clear, it's often related to having a viral infection. Viruses that have been linked to Bell's palsy include viruses that cause:

• Cold sores and genital herpes (herpes simplex)
• Chickenpox and shingles (herpes zoster)
• Infectious mononucleosis (Epstein-Barr)
• Cytomegalovirus infections
• Respiratory illnesses (adenovirus)
• German measles (rubella)
• Mumps (mumps virus)
• Flu (influenza B)
• Hand-foot-and-mouth disease (coxsackievirus)

The nerve that controls your facial muscles passes through a narrow corridor of bone on its way to your face. In Bell's palsy, that nerve becomes inflamed and swollen — usually related to a viral infection. Besides facial muscles, the nerve affects tears, saliva, taste and a small bone in the middle of your ear.