Botox for a downturned mouth: DAO movement versus a fixed mouth-corner position
Depressor anguli oris (DAO) activity can contribute to a mouth corner that pulls downward, but a fixed position or loss of support is another question. Cosmetic DAO use is off-label, with a recent trial studying selected movement and position endpoints.
Botulinum toxin in the depressor anguli oris (DAO) may be discussed when an active downward pull contributes to a downturned mouth corner, but it is not a BOTOX Cosmetic-labeled indication. A corner that sits low at rest can also reflect support, anatomy or skin changes that weakening a muscle may not address. A 2026 single-center study measured oral-commissure position under defined conditions; it does not promise a “mouth lift” for every face or validate a consumer injection map.123
Test the question with movement, not a smile photo alone
The oral commissure is the corner where the upper and lower lips meet. DAO helps pull it downward. A provider can compare the position at rest and during expressions to see whether movement is the dominant issue. A crease next to the mouth, drooping skin, volume loss and an active downward pull may coexist, but they are not the same treatment target. The Botox-versus-filler guide discusses the broader muscle/volume distinction; this decision is about the mouth corner and its function.
| Finding | What it raises | What toxin cannot be assumed to do |
|---|---|---|
| Corner pulls down with expression | DAO activity may be relevant | Correct every resting contour |
| Corner stays low at rest | Support and baseline anatomy need assessment | Add structural volume |
| One side differs from the other | Baseline movement and symmetry matter | Make both sides identical |
| Speech, eating or lip seal are concerns | Function belongs in the decision | Treat the issue as only cosmetic |
The 2026 paper is more informative than a generic anatomy diagram: it included a randomized, double-blind first stage and a nonrandomized second stage, with three-dimensional measures of mouth-corner position and lip asymmetry. Those details also limit interpretation. The two stages do not have the same design, the study is from one center, and measured average changes are not a universal personal result. It is a reason to ask for a documented endpoint, not to select an injection site or dose from the paper.2
Off-label is a precise claim
Current BOTOX Cosmetic labeling lists several facial and neck indications but not DAO treatment for mouth-corner position. A licensed clinician may consider an off-label use of an approved drug; that is different from saying FDA approved that use. The exact product matters, because botulinum-toxin brands and their units are not interchangeable. A practice should identify the product, proposed goal and limits of evidence rather than using “FDA approved Botox” as shorthand for mouth-corner approval.13
The lower face is functionally important. The consultation should discuss pre-existing asymmetry, prior injections, oral function and what would count as an unwanted change. This is not a dose-planning article, and no trial result should be converted into a do-it-yourself route. The gummy-smile guide concerns a different upper-lip/dental-display problem, even though both are near the mouth.
Treat the study’s two stages as two different evidence levels
The 2026 publication had a randomized, double-blind first stage comparing injection locations and a nonrandomized second stage considering an added platysma treatment. They should not be summarized as if the entire publication were one randomized comparison of every possible mouth-corner plan. The three-dimensional measurements establish that the investigators could quantify a position change under their protocol, but a few millimeters on a study measure do not dictate whether a particular reader will notice or value the effect.2
The endpoint is especially sensitive to expression and head position. If a practice uses photographs to explain an offer, ask whether the images show the same facial expression, camera angle and timing. A favorable smile can raise a mouth corner independently of any procedure, while a neutral photograph may conceal how the corner moves during speech. A short video made for clinical documentation—not public marketing—can help the clinician and patient compare the movement they actually care about.
Because oral function matters, request a baseline note on lip seal, speech and any asymmetry rather than only a cosmetic rating. If a patient already has difficulty with one of these functions, the clinician should explain how that changes the decision. “No severe events in a single-center study” does not prove that functional effects cannot occur in other patients or with another product and technique.12
When comparing a DAO plan with filler or another option, insist on one named goal. A muscle-focused plan aims at downward pull; a structural plan might address a resting contour. Combining them without defining which finding each part targets makes it impossible to assess benefit or an unwanted change. A thoughtful consultation may conclude that the fixed anatomy, not active pull, dominates and that toxin is unlikely to satisfy the request.
Use Treomark’s Botox provider hub to find a consultation that documents both the aesthetic goal and functional boundaries. A clear “not a muscle issue” answer can be as useful as a treatment proposal.
Sources
- National Library of Medicine DailyMed. BOTOX Cosmetic prescribing information. Labeled cosmetic indications and boxed warning; DAO/oral commissure is not a listed indication. Accessed .
- Plastic and Reconstructive Surgery. Optimizing injection sites of botulinum toxin type A for oral commissure position. 2026 two-stage single-center study with randomized first stage and nonrandomized second stage; measured 3D commissure position and asymmetry. Accessed .
- U.S. Food and Drug Administration. Understanding unapproved use of approved drugs. Distinguishes clinician off-label use from FDA-approved marketing claims. Accessed .