Bell's palsy: one-sided facial paralysis that usually recovers
Last updated September 3, 2026.
Bell's palsy is a sudden one-sided facial paralysis that looks like a stroke, usually is not one, and usually recovers well. The facial nerve on one side swells inside its bony canal and stops conducting, so half the face droops over hours to a day or two. Most cases follow a viral infection, with herpes simplex reactivation the leading suspect. About 7 in 10 recover completely, and most of the rest recover substantially.
What does it look like, and how do you tell it from a stroke?
The whole half of the face is involved: the eyebrow cannot lift, the eye will not fully close, the forehead stays smooth when you try to wrinkle it, and the mouth droops with drooling from one corner. Taste can go odd, sounds can seem painfully loud on that side, and pain behind the ear often precedes the weakness by a day. The forehead test is the fast discriminator: a stroke affecting the face usually spares the forehead (you can still raise both eyebrows), while Bell's palsy takes the forehead too. That said, any sudden facial weakness deserves urgent assessment rather than home diagnosis, because the cost of guessing wrong on a stroke is measured in brain tissue.
Why the first 72 hours matter
The one treatment with strong evidence is a short course of oral steroids, typically prednisolone, started within 72 hours of symptom onset; it meaningfully increases complete recovery rates. Antivirals alone do not help, and adding them to steroids is reserved for severe cases by specialist judgment. The other urgent job is eye protection: an eye that cannot close dries out and ulcerates, which can threaten vision, so artificial tears by day, lubricant ointment and taping the lid shut at night are standard from day one. Sunglasses outside and moisture chambers help in dry, windy conditions.
What does recovery look like?
Most people begin improving within 3 weeks, and about 85% show significant recovery by 3 months. Full recovery can take up to 6-9 months. Two quirks can appear as the nerve regrows: synkinesis (moving your mouth makes your eye narrow, or vice versa, from miswired regrowth) and crocodile tears (tearing while eating). Facial physiotherapy and neuromuscular retraining help these. Incomplete recovery or troubling synkinesis is a reason for specialist referral, not just patience.
When is it an emergency?
Sudden facial weakness is stroke until ruled out, so first presentation means same-day emergency assessment, especially with any of: arm or leg weakness, slurred speech, trouble finding words, double vision, or unsteady walking. After Bell's palsy is diagnosed, the new emergencies are eye-related: pain, redness, or blurred vision in the affected eye means possible corneal damage and needs same-day eye assessment. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
How can I tell Bell's palsy from a stroke?
The bedside clue is the forehead: Bell's palsy paralyzes the entire half of the face including the forehead (no eyebrow raise, no forehead wrinkles), while a stroke usually spares the forehead because that area gets nerve supply from both sides of the brain. Stroke also tends to bring arm or leg weakness, slurred speech, or confusion. But the safe rule is that sudden facial weakness gets emergency assessment every time, because only an examination, and sometimes imaging, separates the two reliably.
How long does Bell's palsy take to go away?
The typical arc: symptoms peak within 48-72 hours, improvement starts around 3 weeks, and about 85% of people recover significantly within 3 months. Full recovery can take 6-9 months. Roughly 7 in 10 recover completely even without treatment, and early steroids push those odds higher. Weakness that has not begun improving by 3 months, or any worsening after the first week, warrants specialist review.
Do steroids really help, and what are the side effects?
Yes; steroids are the one treatment with solid evidence, started within 72 hours of onset. A typical course is prednisolone 50-60mg daily for 5 days then tapered, and trials show it meaningfully raises the rate of complete recovery. Ten days of steroids in an otherwise healthy person causes few problems: temporary appetite increase, mood lift or irritability, and mild sleep disruption are the common ones. People with diabetes need closer glucose monitoring over the course.
How do I protect my eye when it will not close?
Aggressively, from day one, because a dry exposed cornea can ulcerate and scar. Preservative-free artificial tears every hour or two while awake, lubricating ointment at night, and tape the eyelid closed for sleep (pharmacies sell hypoallergenic tape; a clinician can demonstrate). Wear glasses or sunglasses outdoors against wind and dust. Any eye pain, redness, or blurred vision is a same-day eye assessment, no exceptions.
Is Bell's palsy caused by stress or a cold draft?
The folk explanations (sleeping in a draft, stress, sitting by an open window) do not hold up. The leading evidence points to viral reactivation, most likely herpes simplex, inflaming the facial nerve inside its narrow bony canal. Stress may contribute indirectly by nudging immune control, but it is not the cause. Bell's palsy is also more common in pregnancy and in people with diabetes, again through biological rather than behavioral routes.
Can Bell's palsy come back, and can both sides be affected?
Recurrence happens in roughly 7-10% of people, sometimes on the other side. Simultaneous two-sided facial paralysis is rare and is not typical Bell's palsy; it raises a different list (Lyme disease, Guillain-Barre, sarcoidosis) and needs prompt specialist investigation. A second episode, or an atypical first one (slow onset over weeks, no improvement by 3 months, other neurological signs), is the trigger for imaging and further workup rather than a repeat of the same plan.