What are the causes of Bell’s palsy?

What are the causes of Bell’s palsy?

Bell’s paralysis, or facial palsy, is a paralysis or severe facial muscular weakness on one side of the face.

It is thought to be due to an inflammation of the nerve that controls the face muscles.

It may be worrying but most people are making a complete recovery.

What is Bell’s palsy?

Bell’s palsy involves, on one side of the face, weakness or paralysis. One morning, symptoms often show up first thing. A person wakes up and finds that one side of their face does not move.

The person may suddenly find they can’t control their facial muscles, usually on one side. The side of the affected face tends to drop. The weakness can also affect the production of saliva and tears, and the sensation of taste.

Many people are afraid they have a stroke, but if the weakening or paralysis just affects the face, Bell’s palsy is more likely.

Every year around 1 in 5,000 people develop Bell’s palsy. It is classed as a relatively rare condition.


Most muscles on the face and parts of the ear are controlled by the facial nerve. The facial nerve passes through a small gap of bone between the brain and the face.

If the facial nerve is inflamed, it can either press on the cheekbone or pinch in the narrow gap. This can cause damage to the nerve protection cover.

If the nerve ‘s protective coverage gets damaged, the signals that travel from the brain to the muscles in the face may not be properly transmitted, leading to weakened or paralyzed facial muscles. This is Bell’s palsy.

The exact reason for that is unknown.

This can result when the nerve is inflamed by a virus, usually the herpes virus. This is the same virus that causes the genital herpes and cold sores.

Other viruses linked to Bell’s palsy include:

  • chickenpox and shingles virus
  • coldsores and genital herpes virus
  • Epstein-Barr virus, or EBV, responsible for mononucleosis
  • cytomegalovirus
  • mumps virus
  • influenza B
  • hand-foot-and-mouth disease (coxsackievirus)

Bell’s palsy risk factors

A pregnant woman sleeping
Women who are in the last trimester of their pregnancy or who have just given birth may be at risk from Bell’s palsy.

Some risk factors have been established.

Migraine and facial and limb weakness were found to be linked. A 2015 study found that migraine patients may have a higher risk of Bell’s palsy.

The condition more commonly affects:

  • people aged 15 to 60 years
  • those with diabetes or upper respiratory diseases
  • women during pregnancy, especially in the third trimester
  • women who gave birth less than 1 week ago

Bell’s palsy affects men and women equally.


Most people will recover within 1-2 months from Bell’s palsy, especially those who still have some degree of movement in their facial muscles.

A hormone treatment called prednisolone can accelerate recovery. A study showed that prednisolone would substantially reduce the severity and frequency of the symptoms after 12 months if administered within 72 hours of onset.


This drug cuts down on inflammation. This helps to speed up recovery of the nerve affected. Prednisolone prevents the release of inflammatory substances, such as prostaglandins and leukotrienes, into the body.

Patients take it by mouth, usually two tablets a day for 10 days.

Possible side effects include:

  • abdominal pain, bloating
  • acne
  • difficulty sleeping
  • dry skin
  • headache, dizziness (spinning sensation)
  • increased appetite
  • increased sweating
  • indigestion
  • mood changes
  • nausea
  • oral thrush
  • slow wound healing
  • thinning skin
  • tiredness

These side effects normally get better after a couple of days.

A lady having breathing difficulty
An allergic reaction to prednisolone, such as difficulty breathing, should immediately be reported to a healthcare professional.

Any allergic reaction to prednisolone should immediately be reported to your doctor.

Allergy symptoms may include:

  • hives
  • breathing difficulties
  • swelling of the face, lips, tongue or throat

When the patient feels dizzy or drowsy they should refrain from driving heavy machinery or operating it. Since this symptom may not appear immediately it is recommended to wait a day before driving or operating machinery.

Doctors usually cut the dose gradually to the end of the steroid medication course. That helps to prevent symptoms of withdrawal, such as vomiting or fatigue.

Eye lubrication

If the patient does not blink properly the eye is exposed and tears evaporate. Some patients will experience decrease in production of tears. Both of these can increase the risk of eye damage or infection.

Artificial tears can be prescribed by the doctor in the form of eye drops and an ointment too. During the waking hours the eye drops are usually taken while the ointment is applied before going to sleep.

Patients who can not properly close their eyes while they are sleeping will need to use surgical tape to keep it shut. Patients experiencing worsening eye symptoms should seek immediate medical help. If you can’t get your doctor, go to your nearest hospital’s Emergency Department.


An antiviral, such as acyclovir, may be taken alongside prednisolone in some cases; however, there is weak evidence that they may help.

Care at home

Facial exercises: As the facial nerve begins to recover, tightening and relaxing facial muscles can help strengthen them.

Dental care: If there is little or no feeling in the mouth it is easy for food to build up leading to decay or gum disease. Brushing and flossing can help prevent this.

Problems with eating: If there are difficulties with swallowing, the individual should chew food well and eat slowly. Choosing soft foods, such as yogurt can also help.

OTC pain relief: To ease any discomfort. Some pain relief medications may be purchased online, including ibuprofen and Advil.


The facial nerves control blinking, eye opening and closing, smiling, salivation, lacrimation (the production of tears), and frowning. They also connect with the muscles of the stapes, a bone in the ear involved in hearing.

As in Bell’s palsy, the following symptoms can occur when the facial nerve malfunctions:

  • sudden paralysis/weakness in one side of the face
  • difficulty closing one of the eyelids
  • irritation in the eye because it does not blink and becomes too dry
  • changes in the amount of tears the eye produces
  • drooping in parts of the face, such as one side of the mouth
  • drooling from one side of the mouth
  • difficulty with facial expressions
  • sense of taste may become altered
  • an affected ear may cause sensitivity to sound
  • pain in front or behind the ear on the affected side
  • headache


The Bell’s Palsy Association in the United Kingdom recommends the following exercises:

Facial workout

  • Sit relaxed in front of a mirror
  • Gently raise the eyebrows, using the fingers to help, if needed
  • Pull the eyebrows together and frown
  • Wrinkle the nose
  • Breathe in deeply and flare the nostrils
  • Try to move the corners of the mouth outward
  • Pull one side of the mouth up, then the other, to form a smile
  • If you used your fingers, see if you can keep the smile after removing them

To close the eye

  • Keeping the head still, look down with your eyes only
  • Place one index finger gently over one eyelid to hold it closed
  • With the other hand, pull the eyebrow up slightly, massaging along the browline to prevent stiffness
  • Without using the hands, gently try pressing the eyelids together
  • Hold the eyes half open


The American Medical Association ( AMA) says treatment is most effective when given early, so patients should see their doctor as soon as symptoms develop.

Diagnosing Bell’s palsy is often an elimination process. The doctor will look for evidence of other conditions, such as a tumor, Lyme disease, or stroke, that can cause facial paralysis.

They will inspect the head , neck and ears of the patient. They will also evaluate the facial muscles to determine if any other nerves are affected, apart from the facial nerve.

If it can exclude all other factors, the doctor can diagnose Bell’s palsy.

If the diagnosis is still uncertain, a specialist or otolaryngologist can refer the patient to an ear, nose , and throat (ENT). The patient should be assessed by the expert who will also order the following tests:

  • Electromyography (EMG): Electrodes are placed on the patient’s face. A machine measures the electrical activity of the nerves and the electrical activity of a muscle in response to stimulation. This test can determine the extent of nerve damage, as well as its location.
  • MRI, CT scans, or X-rays: These are good at determining whether other underlying conditions are causing the symptoms, such as a bacterial infection, skull fracture, or a tumor.


The majority of patients undergo full recovery within 9 months. Many that haven’t had more serious nerve damage and will require more care.

That may include:

Mime therapy: This is a kind of physical therapy. A series of exercises are taught to the patient which strengthen the facial muscles. This usually leads to better coordination and a broader range of motion.

Plastic surgery: This may improve facial appearance and symmetry. Some patients experience enormous benefit if they are able to smile again. It does not fix the problem with the nerves.

Botox: Botox injections will relax the tight facial muscles in the affected side of the face and reduce any unnecessary muscle contractions.


Many people are making a full recovery from Bell’s palsy. But, if there is significant damage to the facial nerve, several complications can arise including:

Misdirected re-growth of nerve fibers: Nerve fibers re-grow in an irregular manner. It can contribute to excessive muscle contractions. When trying to smile a patient may involuntarily close one eye. The issue may be the other way round-the side of the mouth lifts involuntarily when the person closes one eye.

Ageusia: A chronic taste loss.

Gustatolacrimal reflex: Also known as tear syndrome of the crocodile. As the patient eats, they will shed tears in their ears. It eventually goes away. In some rare cases the problem may last longer.

Ulceration of the cornea: The protective and lubricating tear film of the eye may become ineffective when eyelids can not be completely shut. That can result in drying of the cornea. The risk of corneal drying is even higher if Bell’s palsy has also caused tear production to decrease. Corneal ulceration can lead to corneal infection, leading to severe vision loss.