One side of the mouth drooping is most commonly caused by Bell’s palsy, a temporary paralysis of the facial nerve that affects roughly 40,000 Americans each year. But before exploring how to fix it, you need to rule out something far more urgent: a stroke. If the drooping came on suddenly and is accompanied by arm weakness or slurred speech, call 911 immediately. Stroke treatments work best when given within three hours of the first symptoms.
Once a stroke has been ruled out, the path to fixing mouth drooping depends entirely on what’s causing it. Most cases improve significantly with medication, targeted exercises, or both.
Rule Out a Stroke First
The CDC recommends using the FAST test anytime you notice sudden facial drooping. Ask the person to smile and check whether one side of the face droops. Ask them to raise both arms and watch for one drifting downward. Have them repeat a simple phrase and listen for slurred or strange-sounding speech. If any of these signs are present, call 911 and note the exact time symptoms started, because that information helps doctors choose the right treatment.
A key difference: stroke typically affects the lower half of the face on one side, while the forehead still works because it receives nerve signals from both sides of the brain. Bell’s palsy, by contrast, usually paralyzes the entire half of the face, forehead included. If you can’t raise your eyebrow or close your eye on the affected side, Bell’s palsy is more likely. But this distinction isn’t foolproof, and emergency evaluation is the only way to be certain.
Bell’s Palsy: The Most Common Cause
Bell’s palsy happens when the facial nerve on one side becomes inflamed, usually from a viral infection. The nerve swells inside a narrow bony canal in the skull, and the resulting compression disrupts signals to the muscles that control your smile, your ability to close your eye, and your forehead movement. Most people wake up with it or notice it developing over a few hours.
The good news is that the majority of Bell’s palsy cases resolve on their own. About 70% of people recover completely without treatment, and that number climbs higher with prompt medication.
Medication Within the First Few Days
Oral corticosteroids are the first-line treatment. A typical course involves taking a moderate dose for five days followed by a five-day taper. Starting this early in the disease course is important because the medication reduces nerve swelling during the critical window when compression is doing the most damage. Doctors sometimes add an antiviral medication alongside the steroid, particularly in cases of severe paralysis.
Facial Exercises That Actually Help
Neuromuscular retraining is the gold standard for rehabilitation after facial nerve damage. Unlike generic “face yoga,” these exercises are designed to rebuild the brain’s connection to specific facial muscles through slow, controlled, symmetrical movements. The goal isn’t to force the muscles to work harder. It’s to retrain them to fire correctly without triggering unwanted movement in other parts of the face.
A common problem during recovery is synkinesis, where trying to smile also causes the eye to squint or the nose to scrunch. Retraining addresses this directly. For example, if smiling triggers involuntary eye movement, you practice a small, balanced smile in front of a mirror, stopping the instant you notice any twitching around the eye. Over time, this teaches the brain to isolate the smile movement cleanly.
Other specific techniques include:
- Eye closure practice: Direct your gaze downward at a target while attempting to close your eyes. Using a hand mirror held at chest level, focus on watching your own pupil while trying to close the eyelid.
- Quick stretch activation: A brief downward stretch of the forehead muscle just before attempting to raise it can help jump-start the movement.
- Reflex-triggered movement: Automatic actions like sniffing can stimulate the muscle group that lifts the area around your nose, helping initiate movements you can’t yet perform voluntarily.
Plan on about 30 minutes of daily practice at home. Movements should be gentle and never forced. Aggressive exercises, like chewing gum vigorously or repeatedly puffing your cheeks as hard as possible, can actually worsen synkinesis by reinforcing sloppy nerve connections. Working with a therapist trained in facial neuromuscular retraining, even for just a few sessions, gives you a personalized program and helps you avoid counterproductive habits.
Protecting Your Eye During Recovery
When the facial nerve is damaged, the eye on the affected side often can’t close fully. This leaves the cornea exposed to drying, irritation, and potentially serious damage. Keeping the eye protected is just as important as treating the drooping itself.
Use preservative-free artificial tears throughout the day and a thicker eye ointment at night. Taping the eyelid shut while sleeping prevents the cornea from drying out overnight. A moisture chamber (essentially a clear shield that fits over the eye area) helps retain humidity around the eye during the day. In more severe cases, doctors can temporarily weigh down the upper eyelid with a small adhesive gold weight or use targeted injections to induce a partial droop in the upper lid, keeping the eye covered while the nerve heals.
Cosmetic Options for Persistent Asymmetry
If full recovery doesn’t happen, or if residual asymmetry remains after the nerve heals, there are effective ways to rebalance the face. Botulinum toxin injections can relax an overactive muscle on the unaffected side that pulls the mouth higher than the weakened side, creating a more symmetrical smile. Dermal fillers can restore volume on the drooping side, reducing the visual difference between the two halves of the face. These aren’t permanent fixes, requiring touch-ups every few months, but they offer meaningful improvement without surgery.
Surgery for Permanent Paralysis
When the facial nerve is permanently damaged and won’t recover on its own, surgical options exist to restore movement. Cross-facial nerve grafting is one of the most effective approaches. A surgeon identifies a healthy nerve branch on the working side of the face, one that produces a natural smile without triggering extra movement in the eye or nose. A nerve segment is then harvested from the lower leg and used as a bridge, connecting the healthy nerve to the paralyzed side.
This procedure is unique in its ability to restore spontaneous, emotionally driven smiling rather than just voluntary movement. The trade-off is patience: facial movement won’t emerge until 9 to 12 months after surgery, the time required for nerve fibers to slowly grow across the graft. Some patients need a second-stage procedure where a muscle from the thigh is transplanted to the face and connected to the new nerve supply.
Less Common Causes Worth Knowing
While Bell’s palsy accounts for most cases of sudden mouth drooping, other conditions can look similar. Myasthenia gravis is an autoimmune disorder that causes fluctuating muscle weakness, and it occasionally presents as facial drooping or a droopy eyelid on one side. The hallmark is that symptoms are mild or barely noticeable in the morning and worsen throughout the day or after sustained muscle use, like a long drive. If your drooping seems to come and go or gets notably worse by evening, mention this pattern to your doctor because it points toward a different diagnosis requiring different treatment.
Other possible causes include infections like Lyme disease, tumors pressing on the facial nerve, ear infections that spread to the nerve, and traumatic injuries. Each has its own treatment path, which is why getting a proper diagnosis matters before pursuing any specific fix.