Upper Lip Horizontal Line and Neuromodulator Treatment
The horizontal line that forms above the upper lip when smiling is called the Upper Lip Horizontal Line (ULHL), and yes, neuromodulators like botulinum toxin can effectively treat this dynamic facial line, though this represents an off-label cosmetic application rather than a medical indication.
Understanding the ULHL
The ULHL is a dynamic facial line appearing during smiling that affects approximately 13.8% of the population, with a strong female predominance (78%). 1 This line is not age-related and can appear in children and young adults, distinguishing it from typical aging-related wrinkles. 1
Anatomical Characteristics Associated with ULHL
Patients presenting with ULHL typically demonstrate specific facial features:
- Shorter upper lip length 1
- Deeper lip sulcus (concavity of the upper lip) 1
- Longer mid-face height 1
- Shorter lower facial height 1
- Greater prevalence of gummy smile 1
The ULHL prevalence shows no correlation with age or malocclusion type. 1
Neuromodulator Treatment Approach
Mechanism and Efficacy
Botulinum toxin type A works by blocking acetylcholine release at the neuromuscular junction, causing temporary muscle relaxation that reduces the appearance of dynamic lines. 2 When applied to the upper lip elevator muscles responsible for ULHL formation, neuromodulators can effectively reduce the line's appearance during smiling.
Treatment for Related Upper Lip Concerns
While specific studies on ULHL treatment are limited, extensive evidence exists for treating related upper lip dynamics, particularly gummy smile (excessive gingival display), which shares anatomical features with ULHL:
- OnabotulinumtoxinA injections into lip elevator muscles produce an 83-85% reduction in gingival display at 2 weeks post-injection 3
- Average doses of 4-6 units per side (total 8-12 units) distributed across 3 bilateral injection sites demonstrate effectiveness 3
- Effects typically last 3-5 months, with gradual return to baseline by 30-32 weeks 4, 5
- Patient satisfaction rates are high, with most patients desiring repeat treatment 3
Injection Technique Considerations
For upper lip concerns, two primary injection approaches have demonstrated efficacy:
- Yonsei point injection: Single-site injection of 3 units bilaterally 6
- Levator labii superioris alaeque nasi muscle injection: Direct muscle targeting 6
Both approaches show equivalent efficacy for reducing excessive upper lip elevation during smiling, with effects visible at 4 weeks and lasting through 24 weeks. 6
Safety Profile
Botulinum toxin injections for cosmetic upper lip applications are safe with minimal adverse events reported. 3, 4 The most common concern is aesthetic dissatisfaction if the effect is too pronounced, which occurred in less than 10% of patients in clinical studies. 3
Important Caveats
- This represents off-label cosmetic use - the FDA-approved indications for botulinum toxin do not specifically include ULHL treatment 7
- Effects are temporary, requiring repeat injections every 3-6 months for maintenance 4, 5
- Individual anatomical variation means that patients with shorter upper lips and deeper lip sulci may respond differently 1
- One patient in clinical studies found the resulting smile unattractive, highlighting the importance of conservative initial dosing 3
Clinical Recommendation
For patients bothered by ULHL, botulinum toxin injection into the upper lip elevator muscles represents a safe, minimally invasive treatment option with high patient satisfaction rates. Start with conservative dosing (4-6 units per side) targeting the hyperactive lip elevator muscles, with effects expected at 2 weeks and duration of 3-5 months. 3, 5 Female patients with short upper lip, lip concavity, and gummy smile are most likely to present with ULHL and may benefit from this intervention. 1