How Can Doctors Tell Bell’s Palsy From Lyme Disease?

Facial weakness can look nearly identical
The history and accompanying symptoms can provide clues
New research may help distinguish Lyme facial palsy from Bell’s palsy

A person wakes up and suddenly cannot smile normally, close one eye completely, or move one side of the face. The diagnosis may quickly be called Bell’s palsy.

But in areas where Lyme disease is common, another possibility deserves consideration: Lyme disease can affect the facial nerve and produce a facial palsy that may look very similar to Bell’s palsy.

The distinction matters because Bell’s palsy and Lyme-associated facial palsy are not the same diagnosis. A September 2026 study specifically examined whether clinical features could help doctors distinguish Lyme neuroborreliosis facial palsy from Bell’s palsy.¹

Why can Lyme facial palsy be mistaken for Bell’s palsy?

Bell’s palsy is an acute peripheral facial nerve palsy without another identified cause. Lyme disease can also involve the seventh cranial nerve, producing weakness or paralysis of the facial muscles.

The facial weakness itself may not reveal the cause. Both conditions can cause difficulty smiling, closing an eye, raising an eyebrow, or controlling one side of the face.

Lyme disease may cause unilateral or bilateral facial palsy. Although bilateral involvement should raise suspicion for Lyme disease and other systemic disorders, many patients with Lyme facial palsy have weakness on only one side.

This means that a unilateral facial palsy should not automatically be assumed to be idiopathic Bell’s palsy, particularly when the patient lives in or has traveled to an area where Lyme disease occurs.

What did the 2026 Bell’s palsy vs Lyme disease study find?

Dos and colleagues conducted a nationwide retrospective study in Denmark involving 683 adults with peripheral facial palsy. Of these patients, 422 had confirmed Lyme neuroborreliosis and 261 had Bell’s palsy.¹

One of the most striking findings was that 23% of patients ultimately diagnosed with Lyme neuroborreliosis had initially been misdiagnosed as having Bell’s palsy.

The researchers evaluated 29 potential predictors and developed a clinical decision-support model called BoB, for “Borrelia or Bell’s?”

Several features helped distinguish Lyme neuroborreliosis from Bell’s palsy:

• Radicular pain
• Positive serum Borrelia burgdorferi IgG
• Symptoms lasting at least 7 days
• Exposure to forest or grassy environments

The resulting decision tree had an accuracy of 0.93, sensitivity of 0.93, and specificity of 0.94 in the study population.¹

The researchers also evaluated a model that did not rely on serum Borrelia IgG, since antibody results may not be available when the patient first presents. In that model, radicular pain and symptom duration of at least 10 days remained important predictors, with similar performance.

These findings are promising, but the authors emphasized that the tool requires external validation before it can be adopted for routine clinical use.

Why is radicular pain an important clue?

Radicular pain is pain arising from irritation or inflammation involving a nerve root. Patients may describe severe shooting, burning, electric, or radiating pain involving the trunk or an extremity.

Radiculoneuritis is a recognized neurologic manifestation of Lyme disease. The CDC advises clinicians to consider Lyme radiculoneuritis in patients with severe limb or truncal radicular pain without preceding trauma when they live in or have traveled to a Lyme-endemic area.²

That makes the combination of facial palsy and otherwise unexplained radicular pain particularly important. The facial weakness may resemble Bell’s palsy, while the additional nerve symptoms suggest a broader neurologic process.

Patients experiencing burning, tingling, numbness, or shooting nerve pain may also benefit from a broader evaluation of neurologic Lyme disease.

Are there other clues that facial palsy may be related to Lyme disease?

No single symptom reliably distinguishes Lyme facial palsy from Bell’s palsy. Instead, clinicians need to consider the entire clinical picture.

Features that may increase suspicion for Lyme disease include:

• Living in or traveling to a Lyme-endemic area
• Outdoor exposure in wooded, brushy, or grassy environments
• A known tick bite, although many patients do not recall one
• An erythema migrans rash
• Fever or flu-like symptoms
• Fatigue
• Headache or neck stiffness
• Muscle or joint pain
• Radicular or shooting nerve pain
• Numbness or tingling
• Facial weakness involving both sides
• Other neurologic symptoms occurring with the facial palsy

The absence of a remembered tick bite or classic bull’s-eye rash does not by itself exclude Lyme disease.

What is the FACE DROPS tool?

The 2026 BoB study is not the first attempt to improve recognition of Lyme-associated facial palsy.

In 2025, McEntire and colleagues published the FACE DROPS clinical risk assessment tool after studying 285 patients, including 76 with Lyme disease-associated facial palsy and 209 with Bell’s palsy.³

The tool incorporates seven clinical features: fever, aches, headache, unusual fatigue, dermatomal or radicular symptoms, ear or postauricular pain, and neck stiffness.

Lyme-associated facial palsy was more often associated with systemic and neurologic findings such as fever, aches, fatigue, headache, radicular symptoms, and neck stiffness. Bell’s palsy was more often associated with ear or postauricular pain.³

Like the newer BoB model, FACE DROPS should not replace clinical judgment. These tools are useful because they reinforce an important principle: the evaluation should extend beyond the appearance of the facial weakness itself.

Can a Lyme blood test distinguish the two conditions?

Lyme serology can provide important supporting evidence, but the result has to be interpreted in context.

The 2026 BoB study found serum Borrelia burgdorferi IgG positivity to be one of the predictors of Lyme neuroborreliosis.¹ However, the authors deliberately created another model without the IgG result because laboratory results may not be available when the patient first presents.

There is another limitation: Lyme disease antibody tests may be negative early in infection before a detectable antibody response has developed. A negative early test therefore does not necessarily exclude Lyme disease.

This is why I do not rely on a single laboratory result to determine whether Lyme disease should remain in the differential diagnosis. I consider the timing of the illness, exposure history, symptoms, examination findings, laboratory results, and alternative diagnoses together.

For a fuller discussion of this diagnostic window, see Can You Have Lyme Disease and Test Negative?

Does facial palsy mean the infection is in the brain?

Not necessarily.

The facial nerve is a cranial nerve, and Lyme disease can affect cranial nerves as part of neurologic Lyme disease. But cranial nerve involvement does not automatically mean that the patient has central nervous system infection.

The CDC specifically notes that neurologic symptoms do not necessarily indicate central nervous system infection in a patient with Lyme disease.²

A lumbar puncture may be useful in selected patients, particularly when meningitis or another central nervous system disorder is being considered, but it is not required for every patient with facial palsy or other neurologic symptoms.

Why does the distinction matter for treatment?

Bell’s palsy and Lyme facial palsy are treated differently.

Corticosteroids are commonly used for idiopathic Bell’s palsy. Lyme-associated facial palsy requires antibiotic treatment. The role of corticosteroids when facial palsy is caused by Lyme disease remains uncertain, which makes identifying Lyme disease before assuming an idiopathic Bell’s palsy diagnosis clinically important.^2,3

Eye protection is also important when facial weakness prevents complete eyelid closure. Patients may require lubricating eye drops, an eye patch, or other measures to protect the cornea while facial nerve function recovers.²

What should doctors ask when someone develops sudden facial paralysis?

The evaluation should not stop with the observation that the patient has a peripheral facial palsy.

Useful questions include whether the patient lives in or recently traveled to a Lyme-endemic area, spends time outdoors, remembers a tick bite or expanding rash, has experienced fever or unusual fatigue, and has headache, neck stiffness, joint or muscle pain, numbness, tingling, or shooting nerve pain.

The September 2026 study adds another useful question: Is there radicular pain?

That symptom emerged as an important predictor even when the researchers constructed a model that did not depend on Lyme antibody results.¹

Sudden facial weakness also has causes other than Bell’s palsy and Lyme disease. Stroke and other neurologic conditions must be considered according to the presentation. New facial paralysis warrants prompt medical evaluation rather than self-diagnosis.

Frequently Asked Questions

Can Lyme disease look exactly like Bell’s palsy?

Yes. Lyme-associated facial palsy can closely resemble Bell’s palsy, particularly when only one side of the face is affected. Exposure history, accompanying symptoms, neurologic findings, and Lyme testing can help distinguish the two.

Can Lyme disease cause facial paralysis on only one side?

Yes. Lyme disease can cause unilateral or bilateral facial palsy. Bilateral facial weakness can increase suspicion for Lyme disease, but unilateral facial palsy does not rule it out.

What symptoms with facial palsy make Lyme disease more suspicious?

Possible clues include tick or outdoor exposure, erythema migrans, fever, fatigue, headache, neck stiffness, muscle or joint pain, radicular pain, numbness, tingling, or other neurologic symptoms. No single feature establishes the diagnosis.

Can a Lyme test be negative when facial palsy first appears?

Yes. Antibody testing can be negative early in Lyme disease before the immune response becomes detectable. Test timing, symptoms, exposure history, examination findings, and alternative diagnoses should be considered together.

Do you need a spinal tap for Lyme facial palsy?

Not necessarily. A lumbar puncture may be useful when meningitis or another central nervous system disorder is suspected, but it is not required for every patient with facial palsy. The decision depends on the overall neurologic presentation and differential diagnosis.

Can a clinical decision tool diagnose Lyme facial palsy?

No. The BoB and FACE DROPS tools were developed to help distinguish Lyme-associated facial palsy from Bell’s palsy, but they do not replace clinical evaluation. The 2026 BoB model still requires external validation before routine clinical implementation.

Clinical Takeaway

Bell’s palsy and Lyme-associated facial palsy can look remarkably similar, particularly when facial weakness affects only one side.

The September 2026 BoB study adds useful evidence that clinicians should look beyond the facial droop itself. Radicular pain, symptom duration, outdoor exposure, and Lyme serology may help identify patients whose facial palsy is associated with Lyme neuroborreliosis.

The finding that 23% of patients with confirmed Lyme neuroborreliosis in this study were initially diagnosed with Bell’s palsy illustrates how easily the distinction can be missed.

When facial palsy occurs in a patient with plausible Lyme exposure or accompanying neurologic or systemic symptoms, Lyme disease deserves consideration before the facial weakness is simply labeled Bell’s palsy.

Related Articles

These articles provide additional information about neurologic Lyme disease, facial nerve involvement, and related diagnostic questions.

Can Lyme Disease Cause Recurrent Facial Paralysis?
Spinal Taps for Lyme Disease: Do You Really Need One?
Lyme Disease Test Accuracy: Timing, Limitations, and Clinical Diagnosis
Lyme Disease Symptoms: Why They Come and Go

References

1. Dos A-HH, Florescu AM, Bryrup T, et al. Borrelia or Bell’s? Development of BoB: a clinical decision support tool to differentiate Lyme neuroborreliosis facial palsy from Bell’s palsy. Ticks and Tick-borne Diseases. 2026;17(5):102704.
2. Centers for Disease Control and Prevention. Clinical Care and Treatment of Neurologic Lyme Disease. Updated March 5, 2025.
3. McEntire CRS, Chung SY, Chang B, et al. FACE DROPS: A Clinical Risk Assessment Tool for Differentiation of Acute Lyme Disease-Associated Facial Palsy From Bell Palsy. Neurology: Clinical Practice. 2025;15(3):e200476.

This article is for informational purposes only and is not intended to provide medical advice, diagnosis, or treatment. New facial weakness or paralysis warrants prompt medical evaluation.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention