Forehead Botox: Efficacy and Risks——Beyond Wrinkle Improvement, the Pitfall of Eyebrow Ptosis
When trying to erase forehead wrinkles, the opposite can happen: eyes appear smaller, facial expression becomes heavy, and you look older——the probability of this occurring is 3.55 times higher than normal.This is not someone's failure story, but a figure demonstrated by a systematic review published in 2023 (Gostimir 2023).
Forehead Botox, when performed appropriately, is a treatment that delivers reliable results. However, if you understand it simply as "injecting makes wrinkles disappear," you may fall into an unexpected pitfall.
This article consolidates information not found in clinic brochures——from mechanisms to real data on side effects. By the time you finish reading, you will be able to judge for yourself whether the procedure you are considering is "the right choice."
What you will learn in this article
- The scientific mechanism by which forehead Botox (botulinum toxin type A) improves wrinkles and its duration of effect
- Confirmed wrinkle-improvement efficacy demonstrated by clinical data and improved patient psychological satisfaction
- "Eyebrow ptosis," "Ptosis"——the incidence rates of serious side effects and the reasons why they occur
- Recommended dosage for safe treatment and site-specific approaches to avoid failure
Why do forehead wrinkles form in the first place?
Forehead wrinkles are not simply a result of "skin aging."
The forehead contains the frontalis muscle, which contracts each time you raise your eyebrows or try to open your eyes wider. When this action is repeated thousands of times daily, creases are etched into the skin——these are the horizontal wrinkles on the forehead.
There is an important point here. The frontalis muscle is, in a sense, a "compensatory muscle." People whose upper eyelids are becoming heavier or those with ptosis tend to use the frontalis muscle to open their eyes, making forehead wrinkles more likely to deepen. In other words,people with deeper forehead wrinkles may have a higher degree of dependence on the frontalis muscle.This directly connects to the "eyebrow ptosis risk" explained later.
The mechanism by which Botox erases wrinkles——a 4-6 month window
Botulinum toxin type A (BTX-A) inhibits the release of acetylcholine from nerve terminals, thereby suppressing muscle contraction. Effects begin to appear 2-3 days after injection and reach peak effect within 1-2 weeks (Berry 2012).
According to meta-analysis of multiple large-scale clinical trials, the duration of effect isan average of 4-6 months(Berry 2012; Cochrane 2021). During this period, frontalis muscle movement is restricted, so wrinkles become shallower and eventually less noticeable.
Regarding repeated administration, there are reports that with continued treatment, muscle atrophy progresses and effects can eventually be maintained with smaller doses (Berry 2012). However——and this is a point many patients overlook——"effects lasting longer" and "increasing dose increases efficacy" are entirely different matters.
Does injecting more make wrinkles disappear?——the pitfall of dosage
I understand the desire to "make it work more strongly." However, this is one of the biggest causes of eyebrow ptosis.
When too much is injected into the frontalis muscle, the entire muscle loses its contractile force. When the frontalis muscle loses the ability to support the eyebrows, the eyebrows physically sag. This iseyebrow ptosis. The space above the eyes narrows, the eyelids appear heavy, and the face looks tired and aged.
Clinically recommended dosage guidelines suggest10–30 unitsfor the entire forehead; however, the appropriate amount varies greatly depending on the patient's muscle mass, sex, and medical history (Berry 2012). While a "standard dose" may exist, "the same amount for everyone" is not correct.
3.55-fold — Real data on adverse effect risk
A 2023 systematic review by Gostimir et al. represents one of the most comprehensive datasets on adverse effects of forehead Botox (Gostimir 2023).
The results were clear.
- Risk ratio for eyelid and eyebrow position abnormalities (eyebrow ptosis, eyelid ptosis): RR 3.55(Gostimir 2023)
- Risk ratio for headache: RR 1.45(Gostimir 2023)
RR 3.55 means what? Compared to placebo (saline), the risk of abnormalities in eyebrow and eyelid position is 3.55 times higher. This is not a "rare side effect"—it is a risk occurring at statistically significant frequency.
You may be thinking right now, "I'll be fine." But this data is not the result from a specific "poorly-skilled clinic." It is integrated data from multiple clinical trials (Gostimir 2023).
Why does eyebrow ptosis occur—anatomical reasons
There are broadly two pathways in the mechanism by which eyebrow ptosis occurs.
① Direct muscle weakness:When the dose administered to the frontalis muscle is excessive, the lifting force of the eyebrow itself is lost.
② Imbalance in antagonist muscles:This aspect is often overlooked. The frontalis muscle (which raises the eyebrows) and the corrugator supercilii and procerus muscles between the eyebrows (which lower the eyebrows) have an antagonistic relationship. When botulinum toxin is injected only into the forehead to weaken the frontalis muscle, the muscles that lower the eyebrows become relatively dominant, causing the eyebrows to drop (Ogilvie 2019).
In other words,injection into the forehead alone carries the risk of disrupting this balance.
Forehead alone vs. forehead + glabella—treatment area determines safety
The answer to this problem has already emerged clinically.
The study by Ogilvie et al. (2019) compared injection into the frontalis muscle alone versus simultaneous injection into the frontalis plus the glabellar complex (corrugator supercilii and procerus muscles). The results showed that simultaneous injection into the forehead and glabellar region is more effective at stabilizing eyebrow position and makes it easier to maintain natural facial expression (Ogilvie 2019).
If you weaken the frontalis muscle, balancing it by simultaneously adjusting the opposing muscles achieves equilibrium——. This is the current standard approach. Even when a patient requests "injection only in the forehead," if a physician recommends concurrent glabellar treatment, this muscle-balance principle underlies the recommendation.
Do results differ by clinic?——Issues of formulation and dilution
"The effect and side effects seem different between clinics even though it's the same Botox"——this perception is correct.
Multiple types of botulinum toxin type A formulations circulate in the market (e.g., onabotulinumtoxinA, abobotulinumtoxinA, etc.), and unit conversion differs by formulation. Additionally, even with the same formulation, the diffusion range varies depending on dilution concentration. The more dilute the preparation, the wider the diffusion and the higher the risk of affecting unintended muscles (Berry 2012).
Safe and reproducible results are achieved only when injection volume, dilution concentration, and injection site align. Information consisting of "how many units were injected" alone is insufficient.
Reliability of efficacy——examining satisfaction data as well
While I have emphasized risks, the effect of properly performed forehead Botox is clinically established.
Multiple trials, including a Cochrane Review (2021), have demonstrated that BTX-A significantly improves dynamic wrinkles on the forehead (wrinkles that appear when making facial expressions). Regarding patient satisfaction, the treatment group has been reported to show improved psychological well-being compared to the placebo group (Berry 2012).
"My face looks brighter" "I no longer appear tired"——these are subjective comments, but behind them lies measurable changes in muscle activity. The problem is not the treatment itself, but ratherappropriate indication assessment and dose setting.
Key points to confirm before your treatment
We recommend confirming the following points during your consultation:
- Type of formulation used and injection units (dilution concentration if possible)
- Opinion on the necessity of concurrent treatment of other areas such as the glabellar region and lateral canthal area
- Current eyebrow position (whether reference lines are confirmed in photographs)
- History or tendency toward eyelid ptosis (evaluation of frontalis muscle dependency)
- Response plan in the event of eyebrow ptosis
Confirming these points is the most practical way to transform the RR 3.55 risk figure into a "number unrelated to me" (Gostimir 2023).
Summary
- Forehead Botox (BTX-A) inhibits frontalis muscle contraction through acetylcholine blockade, with effects lasting an average of 4–6 months (Berry 2012; Cochrane 2021)
- Improvement in dynamic wrinkles is clinically established, and psychological satisfaction improvement in patients is also reported (Berry 2012)
- Risk of eyelid and eyebrow position abnormalities (eyebrow ptosis, eyelid ptosis) is RR 3.55 versus placebo; headache is RR 1.45 (Gostimir 2023)
- The two main causes of eyebrow ptosis are "excessive injection volume" and "collapse of balance between frontalis and antagonistic muscles"
- Concurrent treatment of the glabellar muscle group rather than forehead alone is effective for maintaining balance (Ogilvie 2019)
- The trinity of formulation type, dilution concentration, and injection site determines safety and efficacy (Berry 2012)
References
- Berry MG, et al. Botulinum toxin for wrinkles. J Plast Reconstr Aesthet Surg. 2012.
- Cochrane Systematic Review. Botulinum toxin for facial wrinkles. 2021.
- Gostimir M, et al. Adverse effects of botulinum toxin A for forehead rhytids: systematic review. 2023.
- Ogilvie P, et al. Combined treatment of the forehead and glabellar complex. J Cosmet Dermatol. 2019.
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References
- Kang G, Hsiao Y, Huang J, et al. Aesthetic Durable Forehead Contouring in Asians With Fat Grafting and Botulinum Toxin. Annals of Plastic Surgery. 2019 DOI
- E., R.A., R.M.. Journal of Cosmetic Dermatology. 2015
- Ogilvie P, Rivkin A, Dayan S, et al. OnabotulinumtoxinA for Treatment of Forehead and Glabellar Lines: Subject-Reported Satisfaction and Impact From a Phase 3 Double-Blind Study. Dermatologic Surgery. 2019 DOI
- Camargo C, Xia J, Costa C, et al. Botulinum toxin type A for facial wrinkles. Cochrane Database of Systematic Reviews. 2021 DOI
- Ozdemir Cetinkaya P, Karaosmanoglu N, Özkesici Kurt B, et al. Functional and esthetic effects of botulinum toxin injection into the masseter muscles: evaluation of 80 patients from a dermatological perspective. International Journal of Dermatology. 2025 DOI
About the author of this article
Hiromitsu Nakamura Physician, Ginza Clinic
Zetith Beauty Clinic Ginza, Osaka, and Fukuoka locations
With a track record of research presentations at domestic and international academic conferences, he is involved in technical guidance and education across Zetith Beauty Clinic. He specializes in precision cosmetic medicine based on anatomical principles, pursuing natural results tailored to each individual's bone structure and tissue characteristics.