Understanding DAO Botox and Its Purpose
Botox injections in the Depressor Anguli Oris (DAO) muscle are a popular non-surgical procedure to lift the downturned corners of the mouth [1.2.1]. The DAO is the muscle that pulls the corners of the mouth downward, contributing to a sad or tired expression. By relaxing this muscle with a neurotoxin like Botox, the upward-pulling muscles (elevators) can reposition the mouth corners into a more neutral or slightly lifted position [1.3.6]. The treatment is quick, with results typically appearing within 3 to 7 days and lasting for about 3 to 4 months [1.2.1].
However, this procedure is not without risks. The lower face has a complex network of overlapping muscles responsible for speech, eating, and a wide range of expressions. The proximity of the DAO to these other important muscles increases the risk of complications if the injection is not administered with absolute precision [1.3.1, 1.4.4].
Common and Mild Side Effects
Like most injections, DAO Botox carries a risk of common, mild, and temporary side effects. These are generally localized to the injection site and resolve within a few days [1.2.4].
- Pain, Swelling, or Bruising: Minor tenderness, redness, swelling, or bruising at the injection sites are the most frequently reported issues [1.2.5].
- Headache: Some individuals may experience a headache post-treatment [1.2.5].
- Tenderness: The treated area might feel tender for a short period after the procedure [1.2.2].
Significant Complications from Incorrect Injections
The most concerning risks of DAO Botox arise from injector error, such as improper placement, incorrect dosage, or failure to account for a patient's unique facial asymmetry [1.4.4, 1.5.6]. These mistakes can cause the Botulinum toxin to affect nearby muscles, leading to undesirable and distressing outcomes.
Asymmetrical or Crooked Smile
This is the most-cited complication of DAO Botox gone wrong [1.4.3]. It often occurs when the toxin inadvertently spreads to or is injected into the Depressor Labii Inferioris (DLI) muscle, which is responsible for pulling the lower lip down [1.5.3]. When the DLI on one side is paralyzed, that side of the lower lip won't pull down correctly during a smile, leading to a noticeably uneven or crooked appearance that some describe as looking like they've had a stroke [1.4.5, 1.3.3]. The DAO and DLI muscles are very close and can even overlap, making this an advanced injection that requires a deep understanding of facial anatomy [1.3.6, 1.5.2].
'Frozen' Smile or Functional Difficulties
Over-treating the DAO, or toxin migration affecting other nearby muscles like the risorius, can lead to a 'frozen' or unnatural smile [1.3.1, 1.4.6]. In more severe cases, unintended muscle weakness can cause functional problems [1.4.2].
- Difficulty Speaking or Pronouncing Words: Weakness in the muscles around the mouth can lead to slurring or difficulty with certain sounds [1.4.2].
- Trouble Eating or Drinking: Some patients report difficulty keeping food or liquid in their mouth or using a straw [1.4.2].
- Drooling: A lack of control in the corner of the mouth can sometimes result in drooling [1.2.5].
Rare but Serious Systemic Effects
In very rare instances, the Botulinum toxin can spread far beyond the injection site, causing systemic symptoms that require immediate medical attention. These are more common with therapeutic doses, which are much higher than cosmetic doses, but are still a possibility [1.2.5, 1.3.5]. Symptoms can appear hours or even weeks after treatment and include generalized muscle weakness, vision problems, trouble swallowing or breathing, and loss of bladder control [1.2.2, 1.2.5].
Comparison of Expected vs. Adverse Outcomes
| Feature | Expected & Desired Outcome | Potential Complication | What Causes It |
|---|---|---|---|
| Mouth Corners | A subtle lift, resulting in a more neutral or pleasant resting expression [1.2.1]. | One corner is higher than the other; an exaggerated 'Joker' smile [1.3.3]. | Asymmetrical injection, over-treatment, or incorrect muscle targeted [1.4.6]. |
| Smile | Smile remains natural and symmetrical; no functional impairment [1.5.6]. | A crooked, lopsided, or restricted smile [1.5.2]. | Toxin spreading to the Depressor Labii Inferioris (DLI) or Risorius muscles [1.5.3]. |
| Function | No impact on eating, drinking, or speaking [1.4.2]. | Difficulty with speech, using a straw, or keeping food/drink in mouth [1.4.2]. | Over-dosage or toxin affecting muscles crucial for oral competence [1.4.1]. |
| Sensation | Normal sensation is retained. | A feeling of numbness or unusual muscle weakness [1.4.2, 1.8.3]. | Unintended effect on surrounding muscles or nerves [1.4.2]. |
Mitigating Risks and Correcting Bad Outcomes
The single most important factor in preventing what can go wrong with DAO Botox is the skill and experience of the injector [1.6.1]. A qualified provider, such as a board-certified dermatologist or plastic surgeon, will have extensive knowledge of facial anatomy and can customize the treatment, dosage, and injection placement to your specific muscle structure [1.3.2, 1.4.4].
If a complication like an asymmetrical smile does occur, it is fortunately temporary, as Botox effects wear off in 3-4 months [1.5.1]. In some cases, a skilled injector can correct the asymmetry by carefully injecting a small amount of Botox into the corresponding muscle on the unaffected side to restore balance [1.6.6]. However, this is a corrective measure that also requires significant expertise. For issues of over-treatment, patients unfortunately must wait for the product to wear off naturally [1.6.1].
Visit the Mayo Clinic for more on Botox safety.
Conclusion
While DAO Botox can be an effective treatment for a downturned mouth, its location in a complex muscular region of the face elevates the potential for noticeable complications [1.3.1]. Issues like a crooked smile or functional difficulties are primarily linked to injector error [1.5.4]. Therefore, choosing a highly qualified and experienced medical professional is the most critical step patients can take to ensure a safe procedure and achieve the desired natural-looking results, minimizing the risk of something going wrong.
