Downturned Mouth Corners: The DAO Muscle Explained

Mouth corners that turn down at rest can make a face look sad, stern or tired even when you feel perfectly content. One common contributor is the depressor anguli oris, or DAO, a muscle that pulls the corners of the mouth downward. A small dose of neuromodulator can ease that pull, and filler can rebuild lost support beneath the corners, but each approach has limits and the smile must be protected.

Meet the DAO

The depressor anguli oris is a triangular muscle on each side of the chin. It starts along the lower edge of the jawbone and narrows as it rises to attach at the corner of the mouth. When it contracts, it draws the corner down and slightly out, the movement you make when frowning in disappointment or grimacing.

The DAO works against muscles that lift the mouth corners, mainly the zygomaticus muscles of the cheek. In youth, these forces are fairly balanced. Over time, the lifting side tends to lose some of its advantage while the DAO keeps its strength, so the corners settle lower.

It is rarely just one muscle

Muscle pull is only part of the story. Downturned corners usually reflect several changes happening together:

• Volume loss: the small fat pads beside the mouth and chin shrink, removing support under the corners.
• Bone changes: the jaw and chin gradually recede, so soft tissue has less to rest on.
• Skin laxity: thinner, less elastic skin folds more easily into marionette lines below the corners.
• Tissue descent: early jowls can drag the area beside the mouth downward.
• Natural anatomy: some people have downturned corners from a young age, which is simply their resting expression.

Understanding which of these matter most for you helps decide what, if anything, is worth treating. Our article on nasolabial folds and marionette lines looks at the wider lower-face picture.

Neuromodulator for the DAO

Botulinum toxin type A injected into the DAO can reduce its downward pull, allowing the corners to sit a little more level at rest. The injection is placed low on the muscle, near the jawline and slightly outside the line of the mouth corner, rather than close to the lip.

The change is usually modest: a softer, more neutral resting mouth rather than a lifted smile. Results typically begin within 3 to 14 days and last around three to four months. This approach suits people whose main issue is muscle pull, with reasonable volume still in place.

The risk to your smile

The DAO lies very close to the depressor labii inferioris, which pulls the lower lip down and helps show the lower teeth when you smile. If medicine is placed too close to the mouth or spreads inward, it can weaken this neighbouring muscle. The results can include:

• An uneven or crooked smile, with one side of the lower lip moving less
• Difficulty with speech sounds or with keeping liquid in the mouth
• A lower lip that feels stiff or sits differently

These effects are temporary, but they can last for weeks and can be quite noticeable in conversation. That is why many injectors use a conservative dose for the DAO and why accurate placement matters more than the amount used.

Filler for structural support

When volume loss is the bigger factor, hyaluronic acid filler may help more than muscle relaxation. Small amounts can be placed beneath the mouth corner, along the pre-jowl area beside the chin, or into the chin itself to rebuild a supportive base. This can lift the corner slightly and soften marionette lines.

Filler has its own risks, including swelling, bruising, lumps, infection and, rarely, blockage of a blood vessel. Overfilling the area around the mouth can look heavy or unnatural, so restraint is important. In many people, a combination of a small neuromodulator dose and modest filler gives a more balanced result than either alone. For the general comparison, see filler vs neuromodulator.

Who should not have treatment, or should wait

Injections around the mouth are usually avoided or postponed if you:

• Are pregnant or breastfeeding
• Have a cold sore, infection or inflamed skin near the mouth
• Have a neuromuscular condition such as myasthenia gravis
• Have had a reaction to a botulinum toxin product or hyaluronic acid filler
• Have a recent or sudden change in how your mouth moves, which needs a medical assessment first

That last point is important. A mouth corner that has suddenly started drooping on one side, especially with other facial weakness, can be a sign of a nerve problem such as Bell's palsy or a stroke and needs urgent medical attention, not cosmetic treatment. If you are prone to cold sores, your physician may discuss preventive medicine before filler near the lips. Tell your physician about all medicines, including blood thinners, and do not stop any of them on your own.

Side effects to expect

Most people have mild tenderness, redness or small bumps at the injection sites, which settle quickly. Bruising is common with filler and possible with a neuromodulator. A follow-up about two weeks later lets your physician check symmetry and how your smile moves.

Frequently asked questions

Will treating the DAO make me look happier?

It can make the resting mouth look more neutral. It will not create a smile or change how you express emotion, and the change is usually subtle.

Can a thread lift help instead?

Threads are sometimes used for early jowling, which can affect the mouth corners. They have different risks and limits, and are not suitable for everyone.

Why do my corners look worse in photos?

Overhead lighting and looking down at a phone both deepen the shadows below the mouth. A face-to-face assessment in neutral light gives a more accurate picture.

Is surgery ever the better option?

When significant jowling and skin laxity drive the downturn, a surgical opinion on a lower facelift may be more realistic than injections.

Next steps

A downturned mouth is common and not something anyone needs to correct. If it bothers you, a consultation at HealthPark Medical Aesthetics can look at muscle pull, volume and skin together, explain the trade-offs and help you decide whether neuromodulator, filler, a combination or no treatment makes sense.