Bell’s palsy is a type of temporary facial paralysis or weakness that affects one side of a person’s face. Health experts believe it develops due to viral infection. Some people who have had COVID-19 have also developed Bell’s palsy.

A person’s brain contains 12 pairs of cranial nerves. These nerves connect to different parts of the head, neck, and torso and are responsible for various sensory and motor functions.

Bell’s palsy occurs when there is a problem with one of a person’s cranial nerves. The nerve that Bell’s palsy affects is cranial nerve 7, which has many functions, such as:

  • controlling the muscles on one side of the face, including those a person uses for blinking and certain expressions
  • sending taste sensations from the tongue to the brain
  • sending impulses to the tear ducts, saliva glands, and muscles inside the ear

If this nerve becomes damaged or impaired, it can cause paralysis or weakness in one side of a person’s face.

The exact cause of Bell’s palsy is currently unknown. However, potential causes include viral infection and autoimmune conditions. Some people who developed COVID-19 also showed symptoms of Bell’s palsy.

Read on to learn more about the link between Bell’s palsy and COVID-19, if Bell’s palsy can develop after a COVID-19 vaccine, and when to consult a doctor.

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Information from various case studies suggests that COVID-19 may trigger Bell’s palsy in some people. A review from 2022 found that 46 people developed Bell’s palsy before or after having COVID-19.

The review found that 37% of people in the studies developed Bell’s palsy symptoms first. The remaining 63% developed these symptoms 2⁠–18 days after COVID-19 symptoms began.

However, researchers note that further research is necessary to confirm the link between the two conditions. A study from 2020 suggested that if Bell’s palsy develops alongside COVID-19, it may be due to an autoimmune reaction.

Autoimmune diseases occur when a person’s immune system mistakes healthy tissue for invading organisms. The body’s immune system reacts to what it thinks are harmful foreign bodies and attacks them. This can result in inflammation and swelling.

If a person’s cranial nerve 7 becomes swollen due to an autoimmune reaction, it may cause pressure inside the Fallopian canal.

The Fallopian canal is a bony channel in the skull that allows the cranial nerve to travel to the side of the face. If the cranial nerve swells inside this channel, it may cut off blood and oxygen to the nerve cells. This could prevent the nerve from working properly and lead to facial paralysis.

The clinical trials for both Pfizer-BioNTech and Moderna vaccines found very rare instances of people developing Bell’s palsy after having the vaccination.

In the Pfizer-BioNTech trial involving 43,252 people, four individuals developed Bell’s palsy. In the Moderna vaccine trial involving 30,350 people, three developed the condition. A single person in the control group for the Moderna vaccine also developed Bell’s palsy.

A further study from 2021 found that COVID-19 mRNA vaccines did not have a higher chance of causing Bell’s palsy than other viral vaccines. Another study from 2021 found no association between the Pfizer-BioNTech vaccine and the risk of developing Bell’s palsy.

Research from 2021 discovered that a person has a higher risk of developing Bell’s palsy due to having COVID-19 than from having the COVID-19 vaccine.

The symptoms of Bell’s palsy can vary from person to person. Some people who develop the condition will notice mild symptoms, while others may experience total facial paralysis.

According to the National Institute of Neurological Disorders and Stroke (NINDS), the most common symptom of Bell’s palsy is sudden weakness on one side of the face. Other symptoms of the condition can include:

  • drooping of the mouth
  • drooling
  • being unable to close the eyelids
  • dry eyes
  • excessive tearing in one eye
  • facial pain
  • altered taste
  • intolerance to loud noises
  • facial distortion

Although Bell’s palsy usually only affects one side of the face, in rare cases, it can affect both sides.

A person should speak to their doctor as soon as possible if they notice any signs of Bell’s palsy. Receiving treatment within 72 hours of symptom onset can improve a person’s chances of recovering facial function.

If a person has developed Bell’s palsy for the first time, a doctor may treat them with oral steroids. Steroids have a high chance of being effective against new-onset Bell’s palsy.

However, people who have preexisting conditions may not be able to take steroids. A doctor may prescribe antiviral agents to increase a person’s chances of regaining facial function. However, health experts have not clearly established the benefits of these drugs.

Symptoms of Bell’s palsy generally develop suddenly over 48⁠–72 hours. A person’s symptoms should improve with or without treatment over a few weeks.

The NINDS notes that the outlook for a person who has Bell’s palsy is generally very positive. Research shows that symptoms improve by themselves within 3 weeks in 85% of people. Most individuals who have Bell’s palsy eventually regain typical facial function.

It can take up to 6 months for a person to regain partial or full facial function after having Bell’s palsy. Occasionally, muscle weakness may last longer than this or be permanent.

Bell’s palsy is a form of facial paralysis or weakness. Although it generally only affects one side of the face, it can affect both sides in rare instances.

Researchers are currently unsure of the exact cause of Bell’s palsy. One theory is that autoimmune conditions are responsible.

Studies have indicated that there may be a link between COVID-19 and Bell’s palsy. This may be a result of an autoimmune reaction due to COVID-19. However, further research is necessary to determine the connection between the two conditions.

Current research has not found a significant link between the COVID-19 vaccine and Bell’s palsy. That said, a person is more likely to develop the latter from developing COVID-19 than from having the vaccine.

A person should speak with their doctor if they have any symptoms of Bell’s palsy. Receiving treatment within 72 hours of symptoms developing may improve a person’s chances of recovery.

The outlook for Bell’s palsy is very positive, and individuals should regain full facial function within 6 months. However, some people may have permanent partial facial weakness.