Causes of Bell’s palsy
While the exact cause of Bell’s palsy is unknown, swelling and inflammation of cranial nerve 7 (facial nerve) are usually present in people with symptoms.

Many medical professionals think a viral infection causes the body’s immune system to start targeting the facial nerve, resulting in inflammation and swelling. Viral infections that have been linked to Bell’s palsy symptoms include:

Herpes simplex associated with cold sores and genital herpes

Herpes zoster associated with shingles and chickenpox

The flu virus, specifically influenza B

Human immunodeficiency virus (HIV)

Epstein-Barr virus, associated with mononucleosis (mono)

Sarcoidosis, which causes inflammation of various organs

Hand-foot-and-mouth disease

Mumps virus

Rubella, also called German measles

Adenovirus associated with bronchitis, pneumonia and conjunctivitis

Cytomegalovirus infections associated with chickenpox and mono

PFizer... To date, a small amount of Bell’s palsy cases have been reported in clinical trials of mRNA COVID-19 vaccines, but analyses of the association have so far been conflicting. In the USA, the Federal Drug Administration (FDA) determined that there was no clear causal association for the two mRNA vaccines, BNT162b2 (Pfizer-BioNTech) and the mRNA-1273 (Moderna) vaccines, but ongoing surveillance is recommended. Acute partial facial paralysis is reported as a rare side effect of both vaccines by the European Medicines Agency. Current prescribing information for CoronaVac (an inactivated vaccine) does not list Bell’s palsy as a rare adverse event, however, based on the findings from the study, approval has been obtained to include information on the potential association.

The list of side effects is endless!