ProductsYou feel fine, but people keep asking you what’s wrong. In photos when you were having a good time, your mouth looks flat or a little disappointed. The cause is often one small muscle. DAO Botox relaxes it, which usually helps your face look neutral when you’re doing nothing at all.
The depressor anguli oris, shortened to DAO, is a small triangular muscle that runs from the corner of the mouth down toward the jawline, and its main job is to pull the mouth corner down. A depressor is a muscle that lowers part of the face. When this one dominates, downturned mouth corners become your resting expression. Botox is a neuromodulator, a medication that temporarily reduces the signal from the nerve to the muscle. A small Botox dose usually lets the corner sit higher.
The muscle that pulls the corners down
The DAO pulls your mouth corners down, and the muscles that lift the corners pull against it. One of the lifting muscles is the zygomaticus major, which draws the corner upward when you smile. Both sets of muscles meet at the modiolus, a small spot beside each mouth corner where the muscles around the lips attach.
Years of talking, concentrating and frowning keep the DAO working. Meanwhile, the skin around the mouth gradually loses collagen and elasticity. Collagen is the protein that keeps skin firm. With less collagen, too much strength in the DAO can turn the mouth corners down when you’re expressing nothing.
The DAO also has help from below. It continues down into the platysma, the thin sheet of muscle in the front of the neck, and one study notes that the platysma plays an important role in pulling the mouth corner down.
You can find your own DAO. Make an exaggerated frown, dragging your mouth corners toward your chin, and rest a fingertip just outside and below one corner. The band that tightens under your finger, running down toward the jaw, is the DAO. If cords also pop up in your neck, the platysma is joining in.
What a few units change
A few units in each DAO change how your mouth corners sit when your face is at rest. It’s one of the smallest Botox treatments I do on the face. Botox is measured in units, the standard measure of a dose, and each DAO takes a fraction of what larger facial muscles take. I decide on the dose and injection placement after evaluating how your muscle moves.
What usually changes:
- The corner sits slightly higher at rest, a mouth corner lift measured in millimeters.
- The downward pull softens when you talk or concentrate.
- Your resting face looks neutral or improved.
When the placement is correct, your smile, speech and regular expression are rarely affected. The change is usually slight enough that friends notice you look rested without being able to say why.
Why placement matters more here than almost anywhere
Placement matters because the DAO sits right next to muscles that move your lower lip and lift your smile. Its inner edge overlaps the depressor labii inferioris, a deeper muscle, nearer the center of the lip, that helps turn the lower lip outward. Its outer edge borders the muscles that draw the corner up and sideways during a smile. The same branch of the facial nerve, the nerve that controls your facial expressions, supplies the DAO, the lower lip muscle and the chin muscle, so they all work closely together.
This area is less forgiving than the forehead or crow’s feet.
- Depth. The DAO sits only a few millimeters beneath the skin, and ultrasound studies show its depth varies from person to person, so published technique calls for injecting it superficially, close to the surface.
- The inner boundary. Researchers advise keeping the injections outside a vertical line from the mouth corner, because placing them further in can spread to the lower lip muscle and leave an uneven smile.
- Height. The same number of units placed along the edge of the jaw works less efficiently than units placed higher on the muscle.
One anatomical overview notes that standard injection maps describe an average face that few people match. So I locate your muscle during the exam before deciding where each injection goes. I perform every injection myself, and I’ve injected Botox in New York City since 1992.
Botox Cosmetic’s FDA approval lists four areas: frown lines, crow’s feet, forehead lines and neck bands. The mouth corners aren’t one of them, so treating the DAO is off-label. That means I use an FDA-approved medication in an area its label doesn’t list, if it's medically beneficial. Before treatment, I’ll go over your medical history. You can read who should not get Botox before your visit.
What to watch for after DAO Botox
DAO Botox follows the same timeline as Botox elsewhere on the face, with the change showing over the first days and full results at about two weeks. The effect usually fades over about three to four months, when most patients repeat their treatment.
- The change to look for is how the corner sits at rest, in the mirror or in a candid photo.
- If an issue comes up, it’s most often lip balance. Botox reaching the lower lip muscle by mistake is the most common DAO complication, and it makes the opposite side of the lower lip sit lower.
- Eating and speaking deserve a quick check. Trouble eating has been linked to injection too deep in the muscle, and trouble speaking to Botox spreading into the lower lip muscle. Both settle with time, since these effects fade as the Botox wears off.
On the first treatment, I check your DAO’s strength. Then at the complimentary two-week follow-up, I inject additional Botox if you need it. Some people need a small adjustment. That’s part of the plan, not a sign the first dose failed.
If your smile looks uneven, your lower lip feels heavy, or certain sounds feel harder to make, call the office before the two-week follow-up so I can see it while it’s happening.
When this is not the right treatment
DAO Botox usually isn’t the right treatment when the corner turns down for a reason other than muscle pull.
- Volume loss. When the area beside and below the corner has hollowed, the corner drops because support is missing. Weakening a muscle doesn’t help.
- A deep etched line from the mouth corner to the jaw. This crease is called a marionette line, and when you can see it at rest, it comes from changes in the skin and volume.
- Sagging tissue. When the lower face has loosened and settled, the downturn is partly gravity.
In each case, relaxing the DAO usually helps only a little. If that’s your situation, I’ll tell you at the consultation that Botox isn’t the best choice, even if you came in asking for it. The general difference is laid out in my article on Botox or filler. When filler is the better fit for the corners, I take a conservative approach with hyaluronic acid filler, a gel made from a substance your skin already contains, and place it precisely so the area doesn’t look overfilled.
What it costs
Botox in my office is priced by the treatment area. I’ll go over cost with you at the consultation once I know the muscle is the reason your corners turn down.
FAQ
How many units of Botox for DAO?
It’s a very small number of units on each side. The exact dose depends on how strongly your muscle pulls, so I determine the amount, along with where it goes, at the exam. Any fine-tuning happens at the two-week follow-up.
Will DAO Botox change my smile?
Rarely, when the injection is placed correctly. If Botox reaches the neighboring lower lip muscle, a smile can look uneven for approximately 3 months.
Why does one side of my lower lip look lower after DAO Botox?
Usually because a little Botox reached the lower lip muscle on one side, so the other side pulls lower. To even it out, published guidance describes a tiny dose in the ring of muscle around the lips, on the side sitting lower. Call the office so I can see it before deciding what to do.
Does DAO Botox fix marionette lines?
Usually not on its own. It can soften the downward pull at the mouth corners, but a marionette line from lost volume usually needs filler.
What the first visit involves
Your first visit is a 15-minute consultation that covers your whole face. I’ll evaluate your anatomy, muscle strength and expressions, and explain whether your downturn comes from muscle, volume or loosened skin. I recommend only what is helpful and if Botox isn’t the right fit, I’ll tell you. If it is, I do every injection myself rather than delegating it to a nurse injector, and I’ll see you again at two weeks to fine-tune. When the corners stop pulling down, people usually stop asking what’s wrong. If you’d like to find out whether yours is a muscle problem or a volume problem, request an appointment at our Upper East Side office in Manhattan, and I’ll take a look.
