The Effects and Risks of Forehead Botox — Not Just Smoother Wrinkles, but the Pitfall of Brow Ptosis

The effects and risks of forehead Botox — not just smoother wrinkles, but the pitfall of brow ptosis

Trying to erase forehead lines, only to make your eyes look smaller and your expression heavy and aged instead — the probability of that is 3.55 times the usual.This is not someone's failure story, but a figure shown by a systematic review published in 2023 (Gostimir 2023).

Forehead Botox, when done appropriately, is a treatment from which a reliable effect can be expected. But if you understand it as merely "inject it and the wrinkles disappear," you can fall into an unexpected pitfall.

In this article, from the mechanism to the real data on side effects, we have gathered information not written in the clinic's brochure. By the time you finish reading, you will be able to judge for yourself whether the procedure you are about to undergo is "the right choice."

What you will learn in this article

• The scientific mechanism and duration by which forehead Botox (botulinum toxin type A) improves wrinkles
• The reliable wrinkle-improving effect and the improvement in patients' psychological satisfaction shown by clinical data
• "Brow ptosis" and "eyelid ptosis" — the incidence of these serious side effects and why they occur
• The recommended dose for receiving treatment safely, and the area-by-area approach to avoid failure

In the first place, why do forehead lines form?

Forehead lines are not simply a matter of "the skin having aged."

The forehead has a muscle called the frontalis, which contracts every time you raise your eyebrows or try to open your eyes wide. This motion, repeated thousands of times every day, carves creases into the skin — these are the horizontal forehead lines.

Here is an important point. The frontalis is, in a sense, also a "compensatory muscle." The heavier a person's upper eyelids become, or the more they tend toward eyelid ptosis, the more they use the frontalis to try to open their eyes, so their forehead lines tend to deepen. In other words,the deeper a person's forehead lines, the higher their dependence on the frontalis may be. This connects directly to the "brow ptosis risk" explained later.

The mechanism by which Botox erases wrinkles — the 4-to-6-month window

Botulinum toxin type A (BTX-A) suppresses muscle contraction by inhibiting the release of acetylcholine from nerve terminals. The effect begins to appear 2 to 3 days after injection and peaks in 1 to 2 weeks (Berry 2012).

According to a meta-analysis of multiple large-scale clinical trials, the duration of effect ison average 4 to 6 months(Berry 2012; Cochrane 2021). During this time, the movement of the frontalis is restricted, so the wrinkles become shallower and eventually inconspicuous.

Regarding repeated administration, there are reports that continued treatment advances muscle atrophy so that the effect is gradually maintained even with a smaller amount (Berry 2012). However — and this is a point many patients overlook — "the effect coming to last longer" and "the more you inject, the higher the effect" are entirely different matters.

Will more injections erase the wrinkles? — The pitfall of dosage

I understand the feeling of "wanting it to work more solidly." But this is one of the biggest causes of brow ptosis.

When the dose to the frontalis is too large, the contractile force of the entire muscle is lost. Once the frontalis loses the strength to support the eyebrows, the eyebrows physically drop. This isbrow ptosis. The space above the eyes narrows, the eyelids look heavy, and the face comes to look tired and aged.

The clinically recommended dose guideline is10 to 30 unitsfor the entire forehead, but the appropriate amount differs greatly depending on the patient's muscle mass, sex, and medical history (Berry 2012). Even if a "standard amount" exists, "the same amount for everyone" is not necessarily correct.

3.55 times — the real data on side-effect risk

The 2023 systematic review by Gostimir et al. is one of the most comprehensive sets of data on the side effects of forehead Botox (Gostimir 2023).

The result was clear.

• Risk ratio for malposition of the eyelid/eyebrow (brow ptosis/eyelid ptosis): RR 3.55(Gostimir 2023)
• Risk ratio for headache: RR 1.45(Gostimir 2023)

What does RR 3.55 mean? It means that, compared with placebo (saline), the risk of abnormality in the position of the eyebrow/eyelid is 3.55 times higher. This is not a "rare side effect" but a risk that occurs at a statistically significant frequency.

Right now you may be thinking, "I'll probably be fine." But this data is not the result at a specific "unskilled clinic." It is data integrating multiple clinical trials (Gostimir 2023).

Why brow ptosis occurs — the anatomical reason

There are broadly two routes by which the mechanism of brow ptosis occurs.

(1) Direct loss of muscle strength:When the dose to the frontalis is too large, the strength to lift the eyebrows itself is lost.

(2) Collapse of the antagonist-muscle balance:This one tends to be overlooked more. The frontalis (which raises the eyebrows) and the corrugator/procerus of the glabella (which lower the eyebrows) are in an antagonistic relationship. If you administer Botox only to the forehead and weaken the frontalis, the muscles that lower the eyebrows become relatively dominant, and the eyebrows drop (Ogilvie 2019).

In other words,administration to the forehead alone inherently carries the risk of upsetting the balance.

Forehead alone vs. forehead + glabella — the treatment range determines safety

The answer to this problem has, in fact, already been given clinically.

The study by Ogilvie et al. (2019) compared administration to the frontalis alone with simultaneous administration to the frontalis + glabellar complex (corrugator/procerus). The result showed thatsimultaneous administration to the forehead + glabella is more effective at stabilizing the position of the eyebrows and makes it easier to maintain a natural expression(Ogilvie 2019).

If you are going to weaken the frontalis, you achieve balance by simultaneously adjusting the muscles that oppose it. This is the current standard approach. Even when there is a request to "inject only the forehead," when a physician recommends simultaneous treatment with the glabella, this balance theory is the background.

Do results differ by clinic? — The issue of product and dilution

"It's the same Botox, yet I feel the effect and side effects differ from clinic to clinic" — this feeling is correct.

There are multiple types of botulinum toxin type A products in circulation on the market (e.g., onabotulinumtoxinA, abobotulinumtoxinA, etc.), and the unit conversion differs by product. Also, even the same product changes its range of diffusion depending on the dilution concentration. The thinner the dilution, the wider it diffuses, raising the risk of affecting muscles in unintended areas (Berry 2012).

Only when the three of dose, dilution concentration, and injection site come together can a safe and reproducible result be obtained. "How many units were injected" alone is insufficient as information.

The reliability of the effect — let's also look at the satisfaction data

I have emphasized only the risks, but the effect of properly performed forehead Botox is clinically established.

In multiple trials, including the Cochrane review (2021), BTX-A has been shown to significantly improve the dynamic wrinkles of the forehead (wrinkles that appear when you make an expression). As for patient satisfaction as well, an improvement in psychological well-being has been reported in the treatment group compared with the placebo group (Berry 2012).

"My face came to look brighter," "I'm no longer seen as tired" — these are subjective voices, but behind them are measurable changes in muscle activity. The problem is not the treatment itself, butthe judgment of indication and the setting of the dose.

What you should confirm before you receive it

We recommend confirming the following points at the consultation.

• The type of product used and the dose in units (and the dilution concentration too, if possible)
• The physician's view on the necessity of simultaneous treatment with other areas such as the glabella and crow's feet
• The current position of your eyebrows (whether a baseline line has been confirmed with a photograph)
• Whether there is any history or tendency of eyelid ptosis (assessment of dependence on the frontalis)
• The policy for responding in the unlikely event that brow ptosis occurs

Confirming these is the most realistic way to make the risk figure of RR 3.55 "a figure that has nothing to do with me" (Gostimir 2023).

Summary

• Forehead Botox (BTX-A) suppresses frontalis contraction by inhibiting acetylcholine, and the effect lasts on average 4 to 6 months (Berry 2012; Cochrane 2021)
• The improving effect on dynamic wrinkles is clinically established, and an improvement in patients' psychological satisfaction has also been reported (Berry 2012)
• The risk of malposition of the eyelid/eyebrow (brow ptosis/eyelid ptosis) is RR 3.55 versus placebo, and headache is RR 1.45 (Gostimir 2023)
• The main causes of brow ptosis are the two of "too large a dose" and "collapse of the balance between the frontalis and the antagonist muscles"
• Rather than the forehead alone, simultaneous treatment with the glabellar muscle group is effective for maintaining balance (Ogilvie 2019)
• The trinity of the type of product, dilution concentration, and injection site governs safety and effect (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

1. 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
2. E., R.A., R.M.. Journal of Cosmetic Dermatology. 2015
3. 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
4. Camargo C, Xia J, Costa C, et al. Botulinum toxin type A for facial wrinkles. Cochrane Database of Systematic Reviews. 2021 DOI
5. 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

Author of this article

Hiromitsu Nakamura Ginza Clinic Physician

Zetith Beauty Clinic Ginza, Osaka, and Fukuoka clinics

He has a track record of research presentations at domestic and international academic conferences, and is also engaged in technical guidance and education for Zetith Beauty Clinic as a whole. He specializes in precise aesthetic medicine based on anatomical grounds, pursuing natural results tailored to each person's bone structure and tissue.