The symptoms of Bell's palsy include sudden weakness in your facial muscles. In most cases, the weakness is temporary and significantly improves over weeks. The weakness makes half of your face appear to droop. Your smile is one-sided, and your eye on that side resists closing.
Bell's palsy, also known as acute peripheral facial palsy of unknown cause, can occur at any age. The exact cause is unknown. It's believed to be the result of swelling and inflammation of the nerve that controls the muscles on one side of your face. Or it might be a reaction that occurs after a viral infection.
For most people, Bell's palsy is temporary. Symptoms usually start to improve within a few weeks, with complete recovery in about six months. A small number of people continue to have some Bell's palsy symptoms for life. Rarely, Bell's palsy can recur.
The nerve that controls your facial muscles passes through a narrow corridor of bone on its way to your face. Facial weakness or paralysis may cause one corner of your mouth to droop, and you may have trouble retaining saliva on that side of your mouth. The condition may also make it difficult to close the eye on the affected side of your face.
Signs and symptoms of Bell's palsy come on suddenly and may include:
- Rapid onset of mild weakness to total paralysis on one side of your face — occurring within hours to days
- Facial droop and difficulty making facial expressions, such as closing your eye or smiling
- Pain around the jaw or in or behind your ear on the affected side
- Increased sensitivity to sound on the affected side
- A loss of taste
- Changes in the amount of tears and saliva you produce
In rare cases, Bell's palsy can affect the nerves on both sides of your face.
When to see a doctor
Seek immediate medical help if you experience any type of paralysis because you may be having a stroke. Bell's palsy is not caused by a stroke, but it can cause similar symptoms.
See your doctor if you experience facial weakness or drooping to find out the underlying cause and severity of the illness.
Although the exact reason Bell's palsy occurs isn't clear, it's often related to having a viral infection. Viruses that have been linked to Bell's palsy include viruses that cause:
- Cold sores and genital herpes (herpes simplex)
- Chickenpox and shingles (herpes zoster)
- Infectious mononucleosis (Epstein-Barr)
- Cytomegalovirus infections
- Respiratory illnesses (adenovirus)
- German measles (rubella)
- Mumps (mumps virus)
- Flu (influenza B)
- Hand-foot-and-mouth disease (coxsackievirus)
The nerve that controls your facial muscles passes through a narrow corridor of bone on its way to your face. In Bell's palsy, that nerve becomes inflamed and swollen — usually related to a viral infection. Besides facial muscles, the nerve affects tears, saliva, taste and a small bone in the middle of your ear.
Bell's palsy occurs more often in people who:
- Are pregnant, especially during the third trimester, or who are in the first week after giving birth
- Have an upper respiratory infection, such as the flu or a cold
- Have diabetes
Recurrent attacks of Bell's palsy are rare. But in some of these cases, there's a family history of recurrent attacks — suggesting a possible genetic predisposition to Bell's palsy.
A mild case of Bell's palsy normally disappears within a month. Recovery from a more severe case involving total paralysis varies. Complications may include:
- Irreversible damage to your facial nerve.
- Abnormal regrowth of nerve fibers. This may result in involuntary contraction of certain muscles when you're trying to move others (synkinesis) — for example, when you smile, the eye on the affected side may close.
- Partial or complete blindness of the eye that won't close due to excessive dryness and scratching of the clear protective covering of the eye (cornea).