What causes Bell's palsy?
Bell's palsy occurs because the facial nerve is inflamed and compressed. Exactly what causes this inflammation is not completely understood. It is thought that in many cases, it may be due to an infection with a virus such as Herpes simplex type 1 (which causes cold sores), Herpes simplex type 2 (which causes genital herpes), and Varicella zoster (which causes chickenpox). Other viruses may also cause Bell's palsy, and it can also occur as a complication of pneumonia.