Bell’s palsy is caused by damage to the facial nerve, leading to muscle weakness or paralysis on one side of the face. It begins suddenly and gets worse over the next 48 hours.Anyone can experience Bell’s palsy, though it is more common in pregnant women, those under age 15, and those over 60. There is no cure, though in most cases, it resolves on its own. Some people experience the condition for as long as six months, and in rare cases, the damage is permanent.

Herpes Simplex Virus Type 1

Cold sores are caused by herpes simplex viruses, most often by herpes simplex type 1 (HSV)-1, a common virus that is well-studied. It can remain latent or inactive for a person’s lifetime, but it can also reactivate. When reactivation occurs, it often happens around part of the facial nerve, which can cause Bell’s palsy.Studies have uncovered HSV-1 DNA in facial nerve fluid from affected people, and the virus is known to cause facial paralysis in animals. HSV-1 does not reactivate in everyone and not everyone who has an HSV-1 reactivation will develop Bell’s palsy. It’s more common in immunocompromised people.

Viral Meningitis

Many researchers believe that viral meningitis can also cause Bell’s palsy. Meningitis is inflammation of the membrane covering the brain and spinal cord. When caused by a virus, it usually resolves on its own, but it is still a serious illness that can have many complications, including Bell’s palsy.

Cytomegalovirus

Cytomegalovirus is nother viral infection that can cause Bell’s palsy. It Cytomegalovirus affects as many as 80 percent of adults in the U.S. before age 40.This virus can cause several complications, including Bell’s palsy, and immunocompromised people are at greater risk. It cycles through periods of latency and activity, something that scientists believe may lead to the disorder.

German Measles

German measles or rubella can also cause Bell’s palsy. Rubella is a viral infection that causes a distinct red rash. In most people, it causes mild symptoms, but it is particularly dangerous for a pregnant woman and the development of her baby.A vaccine for rubella is available in most countries, but the virus still exists and is spread through international travel.

Hand-Foot-and-Mouth Disease

The coxsackievirus causes hand-foot-and-mouth disease. The primary symptom is a blister-like rash that can appear anywhere, but most commonly shows up on the hands, feet, and inside the mouth.A small number of people with hand-foot-and-mouth disease develop swelling in the brain or along the spinal cord, which can cause Bell’s palsy.

Mononucleosis

Mononucleosis is an illness caused by the very common Epstein-Barr virus. Most people with mononucleosis experience mild symptoms, like sore throat, headache, fatigue, fever, and swollen lymph nodes. Although uncommon, mononucleosis can cause serious side effects, including nervous system complications, like Bell’s palsy.

Mumps

Mumps is another viral cause of Bell’s palsy. This illness affects the salivary glands, near the ears.Most people with mumps experience mild symptoms, like pain, muscle aches, fever, and headache. Complications are rare but can be serious. The virus can spread through the bloodstream, causing infections in the brain and leading to meningitis and Bell’s palsy.

Neck or Facial Trauma

Physical trauma is also a cause of Bell’s palsy. The symptoms are due to damage to the facial nerve, which runs from the brain stem and around the sides of the face. Any physical trauma to this area — for example, a blow to the side of the head or an automobile accident — can damage the nerves and cause Bell’s palsy.

Diabetes Mellitus

Some medical professionals may not consider diabetes mellitus a cause of Bell’s palsy, but research shows that the two are linked.One study showed that 35 percent of study participants with Bell’s palsy also had diabetes mellitus. This study also demonstrated that diabetes mellitus affected both the presentation and outcome of Bell’s palsy in study participants.

High Cholesterol and Hypertension

Research shows that high cholesterol and hypertension may also be linked to Bell’s palsy. In one study, 28 percent of people with Bell’s palsy also had hypertension and 19 percent had high cholesterol, a larger percentage than in the general population. These preexisting conditions may affect the severity of Bell’s palsy and how well the person recovers.