Frown lines, or glabellar lines, are caused by the repeated contraction of the corrugator and procerus muscles between the eyebrows. These muscles pull the brows inward and downward when you frown or concentrate.
Frown lines are also known as “11s lines” because of their vertical appearance. In your 20s and 30s, these lines tend to appear only when you make an expression. But as your skin loses collagen and elasticity, they may become etched in and fixed, always showing even when your face is neutral.
Angry 11s in the Media
The 11s have long been a focus in beauty blogs, makeover shows, and even memes. They’ve been labelled as “angry 11s”, “resting stress face” and “angry mom creases.”
Social media has coined terms like “Anti-RBF Botulinum Toxin” (RBF = Resting B*tch Face) to describe the emotional softening effect of treating this area — where Botulinum Toxin doesn’t just smooth the skin, but softens how others perceive you.
No one, of course, wants their forehead to say “I’m mad” when they’re just trying to focus.
Upper face anatomy- muscles of facial expression
The Corrugator and Procerus muscles are responsible for the formation of frown lines
Anatomy of the frown lines
The muscles of facial expression responsible for creating frown lines (aka glabellar lines) are the corrugator supercilli and procerus muscles. The action of these muscles is to pull down the inner eyebrow and lower forehead, causing the skin of the glabella to crease. These muscles are often activated when an individual is stressed or unhappy, hence their negative association.
How Botulinum Toxin Treats Frown Lines
Botulinum Toxin works by relaxing the small muscles responsible for pulling your eyebrows together. Once those muscles are softened:
The overlying skin smooths out
The “angry” or intense expression fades
You regain a more relaxed, open look
Note: The treatment doesn’t fill the lines. It prevents the underlying movement that causes them. Over time, this may also help the skin repair itself and prevent lines from deepening. For fixed frown lines, resurfacing treatment such as fractional CO2 laser is required.
Benefits of Botulinum Toxin for Frown Lines
Softens the appearance of the “11s” between your brows
Prevents deeper lines from forming over time
Quick, in-clinic treatment with no downtime
Natural-looking results when done by an experienced doctor
It may help reduce tension-related headaches in some individuals
What Happens During Treatment?
1. Consultation & Facial Mapping
You’ll start with a detailed consultation. We doctor will assess:
How often and strongly you frown (some patients aren’t even aware they do!)
Whether the muscle movement has led to deep static lines
If any related areas (e.g. forehead or brow position) need to be considered for natural results
2. Botulinum Toxin Injection Planning
Your glabella has two main muscles:
Corrugators (pull the brows inward)
Procerus (pulls the central brow downward)
We plan the number of injection points based on your muscle strength and facial dynamics.
If needed, we’ll also discuss whether combining with forehead Botulinum Toxin may enhance balance and brow position.
3. During the Procedure
We clean the area thoroughly
Using a very fine needle, Botulinum Toxin is placed precisely into the mapped muscle points (usually 5 injections total).
The whole procedure takes just a few minutes.
4. Aftercare Tips
Post-treatment care is simple:
Avoid lying flat, vigorous activity, or rubbing the area for 4–6 hours
Mild swelling, redness, or small bumps may appear and resolve within 15–30 minutes
You can return to work or errands immediately
5. What Results to Expect
You may notice a softening in the frown expression within 3–5 days
Full results appear around 10–14 days
With regular treatments, deeper static lines often soften as the skin stops creasing repeatedly
Note: For very deep glabellar lines that are present at rest, your doctor may suggest treatments, like forehead fillers, to improve static lines.
How Many Units of Botulinum Toxin Are Needed for Frown Lines?
Most people need 8-12 units of Botulinum Toxin to treat the glabellar area effectively. This usually includes:
Corrugator muscles (each side): 2-4 units
Procerus muscle (center): 2-4 units
Botulinum Toxin injection points for frown lines (Glabellar lines)
Factors that may affect dosage:
Muscle strength (men often require higher doses)
Depth of the lines
Whether you're combining treatment with forehead Botulinum Toxin for balance
At Bay Aesthetic Clinic, we will factor your anatomy, expression patterns and aesthetic goals into every treatment, so your results look natural.
Risks and Side Effects
While Botulinum Toxin for frown lines is generally safe and well-tolerated when performed by a trained medical professional, there are some potential side effects to be aware of.
Common side effects:
Mild swelling, redness, or tenderness at injection sites
Temporary headache
Minor asymmetry in expression (can be adjusted with touch-up)
Less common risks:
Drooping eyelid or eyebrow (ptosis), especially if injected too low or if Botulinum Toxin migrates into the eyelid
Note: These risks apply to all Botulinum Toxin treatments. To minimise any complications, it’s important to have your treatment done by a doctor who can account for your individual facial profile and aesthetic goals.
Is It Too Early to Start Botulinum Toxin?
You don’t need deep lines to benefit from Botulinum Toxin. Many patients in their late 20s to early 30s choose to treat the glabella as a preventive measure — to stop those lines from forming or becoming permanent. In fact, for the treatment of glabellar lines, it is better to start early, as fixed glabellar lines are difficult to treat.
Early treatment may:
Maintain a youthful, fresh expression over time
Reduce the frequency of frowning
Prevent static lines from developing
Why Choose Bay Aesthetics Clinic to Treat Your Frown Lines?
Our Medical Directors, Dr Bernard Tan and Dr Hoe Ying Min, bring over 20 years of experience in non-surgical aesthetic treatments, with a keen eye for detail and a commitment to natural-looking results.
Botulinum Toxin for frown lines (glabellar lines) at Bay Aesthetics Clinic
With over 10 years of experience in aesthetic treatments, Dr Hoe Ying Min serves as the Medical Director at Bay Aesthetics Clinic. She has extensive hands-on experience in lasers, injectables, body-shaping and skin-rejuvenation procedures, and is known for her careful, personalised approach that aims for natural-looking outcomes.
Bay Aesthetics Clinic and Medispa is a doctor-led clinic located in the Marina Bay Financial Centre that delivers medical aesthetics and medispa treatments in a calm, professional setting. With a focus on safety, visible results and accessibility, the team uses only US FDA and HSA-approved technology, applies a holistic view to beauty and wellness, and avoids hard-selling or pressure tactics.
Open from 11 am daily (until 8 pm Mon-Fri; 6 pm Sat/Sun) and conveniently situated within walking distance of two MRT stations
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B2-12 Marina Bay Link Mall, 8A Marina Boulevard, Marina Bay Financial Center, Singapore 018984
