Causes of Bell's Palsy

Viral infections—such as herpes simplex, herpes zoster (shingles), chickenpox, mumps, mononucleosis (mono), or HIV—and bacterial infections such as Lyme disease or tuberculosis can cause inflammation and swelling of the facial nerve leading to Bell's palsy. A brainstem tumor, skull fracture, or neurological condition caused by chronic disease (e.g., diabetes, Guillain-Barre syndrome) can also lead to Bell's palsy.

Bell's Palsy Risk Factors

Conditions that compromise the immune system, such as HIV, increase the risk for Bell's palsy. Patients who have diabetes are more than 4 times as likely to develop the disorder as the general population. Women who are pregnant have a 3.3 times higher risk for Bell's palsy than women who are not pregnant. During pregnancy, Bell's palsy occurs most often in the third trimester.

Other Bell's palsy risk factors include the following:

  • Bacterial infections such as Lyme disease or typhoid fever, syphillis, tuberculosis, frequent middle ear infections
  • Neurological disorders such as Guillain-Barre syndrome, multiple sclerosis, and neurosarcoidosis
  • Traumatic injury to the head or face
  • Tumors causing nerve compression
  • Viruses such as influenza (the flu), the common cold, or infectious mononucleosis

Publication Review By: Tha T. U, M.D.

Published: 01 Jan 2000

Last Modified: 02 Sep 2015