The most common cause of Bell's palsy is thought to be the herpes simplex virus, which also causes cold sores. Potential other causes of Bell's palsy include the herpes zoster virus (which causes chickenpox and shingles), the virus that causes mononucleosis (called Epstein-Barr), and the cytomegalovirus. When one of these viruses infects the body, it can cause the nerve that controls your facial muscles to become inflamed (swollen).
Bell's palsy is more prevalent among the following people:
- Pregnant women, especially during the third trimester, or who are in the first week after giving birth;
- People who have diabetes:
- Someone who has an upper respiratory infection (cold or flu).
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