Depressor Anguli Oris (DAO)

The depressor anguli oris (DAO) is a small, triangular facial muscle that runs from the jaw up to the corner of the mouth and pulls that corner downward. It is the muscle behind a frown or a downturned, “sad” mouth. Because an overactive DAO can leave the mouth corners turned down even at rest, it is a common target for botulinum toxin, which relaxes the muscle so the corners can sit in a more neutral, lifted position.

At a glance

• What it is: A paired, triangular muscle of the lower face (its name means “that which lowers the angle of the mouth”)
• Where it runs: From the jawbone (mandible) up to the corner of the mouth
• What it does: Pulls the corner of the mouth down and out—the frowning, displeasure expression
• Nerve supply: The marginal mandibular branch of the facial nerve (CN VII)
• Why it matters: An overactive DAO can create a permanently downturned mouth and deepen marionette lines
• Common treatment: Small doses of botulinum toxin to relax it and lift the mouth corners

What is the depressor anguli oris?

The depressor anguli oris is a paired, triangular muscle of the lower face and part of the group of muscles that move the lips and mouth. It arises from the oblique line of the mandible—the jawbone—and its fibres travel upward to converge on the modiolus, the dense, mobile knot of muscle at the corner of the mouth where several facial muscles meet.^[1] It is innervated by the marginal mandibular branch of the facial nerve (CN VII), the same nerve that controls the muscles of facial expression.^[1][2] Anatomically, the DAO is closely related to the platysma of the neck, effectively continuing its downward pull up to the mouth.^[2]

What the DAO does

As its name suggests—depressor (lowers), anguli oris (angle of the mouth)—the muscle’s job is to pull the corner of the mouth downward and slightly outward.^[1] It is one of the face’s frowning muscles, producing the expressions we associate with sadness, displeasure or disapproval. Like all facial-expression muscles it also plays a part in everyday movements of the mouth during speech and eating. In a balanced face, the DAO works in opposition to the muscles that lift the mouth corners, and the two sets keep the mouth in a neutral resting position.

The DAO and a downturned mouth

When the DAO is overactive or its downward pull outweighs the lifting muscles, the corners of the mouth can begin to turn down even when the face is relaxed—excessive DAO tone can produce a chronically unhappy or angry appearance.^[2] Over time this contributes to a downturned mouth and can deepen the marionette lines that run from the corners of the mouth toward the chin. This is a change many people notice with age as the balance between the lifting and lowering muscles shifts and the skin loses support. It is a dynamic pattern—driven by muscle action—which is precisely why relaxing the muscle can help.

Treating the DAO with botulinum toxin

A small, well-placed dose of botulinum toxin type A can relax the DAO so it no longer over-pulls the mouth corners. With the downward tension eased, the opposing lifting muscles can raise the corners into a more neutral, subtly upturned position—softening a downturned or “sad” resting mouth.^[2][3] Products such as Botox and Dysport are used for this purpose. It is a refined lower-face treatment often combined with dermal filler when there is also a deep marionette crease to support. At Revel, this is offered through our neuromodulator treatments.

Safety and why technique matters

The lower face is a technically demanding area. The DAO sits close to muscles essential for smiling and moving the lips, so accurate dosing and precise placement are critical—too much product, or injection in the wrong spot, can affect the smile or lip movement.^[2] For this reason, DAO treatment should be performed only by a qualified, experienced injector with a thorough understanding of lower-face anatomy, after assessing how your muscles move. Botulinum toxin is a prescription treatment in Canada. This entry is educational and does not replace an individual clinical assessment.

Related glossary terms

• Marionette Lines
• Botulinum Toxin Type A
• Botox
• Dysport
• Dynamic Wrinkles
• Dermal Filler
• Revel: Neuromodulator Treatments

Clinical & editorial sources

1. Kenhub. Depressor Anguli Oris Muscle: Origin, Insertion and Action. kenhub.com
2. Sethi N, et al. Anatomy, Head and Neck: Facial Muscles. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. NBK493209
3. Padda IS, Tadi P. Botulinum Toxin. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. NBK557387