What the DAO muscle actually does
The depressor anguli oris – DAO for short – is a small muscle that runs from the jawline up to the corner of the mouth. Its job is to pull the corners of the mouth downward, which is a normal and necessary part of expressions like frowning or showing displeasure.
The muscles that pull the mouth corners up – mainly the zygomaticus major – work against the DAO. As people age, this balance often shifts: the depressor muscles can become relatively more dominant, and the result is a resting mouth expression that looks downturned or subtly sad, even when someone is not frowning at all.
Worth knowing: using a neuromodulator on the DAO for a cosmetic mouth-corner lift is an off-label use, similar to masseter treatment for jaw slimming. It is well-established in practice, just not a formally FDA-approved indication for that specific purpose.
What treating the DAO can actually do
Relaxing the DAO reduces its pull downward, which allows the elevator muscles to have more relative effect without fighting against it. The result is typically a subtle lift at the corners of the mouth and a resting expression that reads as more neutral or content, rather than downturned.
This is a subtle change by design. It is not the same as a surgical lift, and a heavy-handed dose here risks affecting nearby muscles involved in lip movement and speech – this is genuinely one of the areas where a conservative approach matters more than in most places on the face.
What it cannot fix
- Volume loss along the marionette lines. The grooves running from the corners of the mouth toward the chin are often a combination of muscle pull and lost volume – relaxing the DAO addresses the first, not the second.
- Skin laxity or jowling. Loose skin along the jawline is a structural change that a neuromodulator does not address.
- A dramatic smile lift. The change here is a subtle shift in resting expression, not a significant reshaping of how the mouth moves when smiling.
For the volume component specifically, this is often paired with dermal filler along the marionette lines rather than treated with a neuromodulator alone.
Questions people ask
What does DAO Botox actually treat?
It relaxes the muscle that pulls the corners of the mouth downward, which can soften a downturned resting expression and give a subtle lift at the corners.
Will this fix my marionette lines?
Partially. It addresses the muscle pull contributing to the look, but volume loss along those lines usually needs filler as well for a complete result.
Is treating the DAO risky?
It sits close to muscles involved in lip movement, so it needs a conservative, precise approach more than most areas. This is a technique and dosing consideration, not a reason to avoid it.
How noticeable is the result?
Subtle by design – a softened resting expression rather than a dramatic reshaping of the mouth.
Noticing a downturned resting expression?
A nurse practitioner-led practice in Scottsdale, Arizona.
