10 Symptoms of Bell's palsy

Bell's palsy is an acute peripheral facial nerve disorder that causes unilateral weakness or paralysis of the muscles of facial expression, including the forehead, eyelid, cheek and mouth. Typical features include inability to fully close the eye with associated dryness, loss of taste on the affected side, impaired smiling, drooling and facial asymmetry. New-onset facial paralysis warrants prompt medical evaluation to confirm the diagnosis and exclude other serious causes such as stroke.

1. Weak facial muscles on one side

Twelve cranial nerves connect the brain with structures of the head and neck; the seventh cranial nerve, the facial nerve, provides motor control of the facial muscles and contributes to facial sensation. Inflammation of the facial nerve can cause sudden unilateral weakness or paralysis of the face, which is the defining feature of Bell’s palsy. The exact cause remains unknown, but a viral origin is suspected because many cases follow an upper respiratory infection, and diabetes is a recognized risk factor.

2. Inability to close one eye

Each side of the face is supplied by a facial nerve (cranial nerve VII); if one nerve is impaired, the muscles on that same side become weak. The orbicularis oculi, the muscle that encircles the eye and produces eyelid closure, is often affected in Bell’s palsy, which can make closing the eye difficult.

3. Dry eye

Patients with Bell’s palsy may not be able to fully blink or close the affected eye, which increases tear evaporation and can cause exposure-related dry eye. If untreated, this can lead to ocular irritation, corneal damage and potential vision impairment. Preventive measures include frequent preservative‑free artificial tears, nighttime lubricating ointment, moisture protection or an eye patch, and prompt ophthalmology follow‑up.

4. Asymmetrical (crooked) smile

The buccinator, a cheek muscle innervated by the facial nerve, flattens the cheek and retracts the mouth’s angle to help keep food positioned during chewing. It also contributes to facial expressions such as smiling and whistling and assists infants with suckling. When the facial nerve is compromised, the buccinator weakens, often resulting in impaired or asymmetric smiling.

5. Drooling

The facial nerve innervates the orbicularis oris, the circular muscle that surrounds the lips and closes the mouth. Analogous to the orbicularis oculi around the eye, the orbicularis oris—commonly called the “kissing muscle”—is essential for lip closure and functions such as playing brass instruments. Weakness of this muscle can impair lip seal and lead to drooling.

6. Loss of Taste

The chorda tympani, a branch of the facial nerve (cranial nerve VII), transmits taste from the anterior two-thirds of the tongue and carries parasympathetic fibers that stimulate salivary secretion. When the facial nerve is compromised, a person may lose the ability to perceive sweet, sour, salty, bitter and umami (savory) tastes—a condition called ageusia. Because the posterior third of the tongue is innervated by the glossopharyngeal nerve, disorders such as Bell’s palsy typically affect taste only in the front portion of the tongue.

7. Difficulty raising an eyebrow

The frontalis muscle elevates the eyebrows. When the facial (VII) nerve is injured or inflamed, this muscle may be weakened or paralyzed; as a result, people with Bell’s palsy often cannot raise the eyebrow on the affected (ipsilateral) side.

8. Symptoms which vary by individual

Symptoms of Bell’s palsy vary in severity. Some patients experience mild facial weakness, while others have marked paralysis of the muscles on the affected side. Occasionally there is pain in or behind the ear and increased sensitivity to sound (hyperacusis) on the same side. These ear-related symptoms reflect involvement of a facial nerve branch that passes through the ear but are uncommon.

9. Facial distortion

Symptoms of Bell's palsy typically begin suddenly and reach their worst within 48 hours, though some facial weakness or asymmetry may persist. Affected individuals often report difficulty speaking, eating, and drinking, along with jaw pain and numbness or reduced sensation on the involved side of the face.

10. Symptoms in other areas of the body

Although Bell’s palsy primarily affects the face, some patients report additional symptoms such as headache, neck pain, memory difficulties, impaired balance or clumsiness, and occasional weakness in an arm or leg on the same side. These features can occur with Bell’s palsy but are not readily explained by isolated facial nerve dysfunction and should prompt further evaluation to exclude other causes.