How to Treat Forehead Lines with Botox Without Freezing Facial Expression

In aesthetic medicine, forehead lines are one of the most frequently requested areas for botulinum toxin (Botox) treatment. While patients often seek a smoother forehead to reduce signs of ageing, overtreating this area can lead to a lack of natural expression and a stiff or unnatural look. The key to effective treatment lies in understanding the anatomy and function of the frontalis muscle, as well as the delicate balance between facial muscle groups that control eyebrow movement and upper face dynamics.

This blog explores how medical aesthetic practitioners can treat forehead wrinkles with Botox while maintaining natural expression.

Understanding the Frontalis Muscle

The frontalis muscle is the only elevator in the upper third of the face. It lifts the eyebrows and forms horizontal forehead lines, especially during expressions like surprise or concern. Anatomically, it originates from the galea aponeurotica and inserts into the skin above the eyebrows, with no bony attachments. This structural detail makes it particularly sensitive to the effects of botulinum toxin injections.

The muscle is not uniform in function. The upper fibres contribute to line formation, while the lower fibres are more directly involved in eyebrow elevation. This distinction matters clinically, as overtreating the lower frontalis, especially in patients who use it to compensate for eyelid hooding or dermatochalasis, may result in brow heaviness or even ptosis.

Sex-based anatomical variation is also relevant. Male patients often have a stronger, more fibrous frontalis that extends further into the scalp, which may require higher doses of Botox. Female patients typically have a narrower frontalis and a more defined brow arch, requiring a more tailored approach to preserve aesthetic proportions. In older patients, thinning of the skin and loss of underlying fat layers increase the visibility of forehead lines, while simultaneously heightening the risk of overcorrection.

Facial Muscles: Elevators and Depressors

Successful treatment of forehead lines with botulinum toxin depends on understanding the antagonistic relationship between the frontalis (elevator) and surrounding depressor muscles-  including the corrugator supercilii, procerus, and orbicularis oculi. When treating with Botox, clinicians must consider these facial muscle vectors to preserve natural eyebrow movement and prevent unwanted aesthetic outcomes.

This concept is known as botulinum rebalancing. By reducing the activity of the procerus and corrugator muscles, for instance, aesthetic clinicians can create a natural lift in the medial brow by allowing the frontalis to dominate. However, if only the frontalis is treated without modulating the depressors, patients may experience a drop in brow position or a flat, heavy appearance.

Injection Technique: Planning, Landmarks, and Safety Considerations

The ideal outcome of a forehead Botox treatment is softening of dynamic lines without erasing the patient’s ability to express themselves. This starts with a dynamic assessment. Observing how the brow moves during conversation and expression helps determine the most active regions of the frontalis muscle and informs safe and effective injection placement.

Most patients require between 10–20 units (if using Botox or Bocouture), or 25–50 Speywood units (for Azzalure). Men and patients with larger or more active foreheads often require higher doses. For women, a gentle V- or M-shaped injection pattern helps preserve the natural arch of the brow. In men, a straighter, horizontal placement may be more suitable to maintain masculine features.

All injections should maintain a 2 cm safety margin above the orbital rim to reduce the risk of brow ptosis. The toxin should be placed into the mid-depth of the frontalis, which sits approximately 3–5 mm beneath the skin surface. Injecting too superficially may lead to poor uptake, while deeper injections carry a higher risk of diffusion into adjacent structures.

Common Complications in Forehead Botox – and How to Avoid Them

Like any aesthetic procedure, forehead Botox treatments carry potential complications. Brow heaviness is among the most common and usually results from over-relaxation of the lower frontalis, particularly in patients who rely on this muscle to compensate for eyelid droop.

Another frequently encountered issue is asymmetrical brow elevation, or “Spock brow,” which occurs when the lateral frontalis remains active due to inadequate treatment. This can usually be corrected with a small additional dose of 1–2 units of toxin in the overactive area.

The most serious but rare complication is eyelid ptosis, which can occur if the toxin diffuses into the levator palpebrae superioris. This is more likely in patients with low-set brows, pre-existing eyelid issues, or incorrect injection technique near the orbital rim.

Patient selection and consultation are critical to preventing such outcomes. Older patients or those with dermatochalasis, previous blepharoplasty, or prominent brow descent should be approached with caution, and treatment modified or avoided accordingly.

The Importance of Clinical Reasoning

Treating the forehead should never be viewed as a “beginner” procedure. In fact, it is one of the most nuanced areas to treat, precisely because of the frontalis’s unique anatomical role and its interaction with adjacent muscle groups.

Rather than aiming to erase all lines, the goal of forehead Botox should be to soften excessive movement while preserving a patient’s natural ability to express emotion. Starting conservatively, and reassessing after two weeks, allows for incremental adjustment and significantly reduces the risk of overcorrection. Patients should also be educated on the difference between dynamic and static lines, and why deeper, etched rhytids may require complementary treatments like microneedling, skin boosters, or polynucleotides in addition to Botox.

This layered, reflective approach reinforces the importance of clinical judgement in aesthetic practice. As with any injectable treatment, it’s not just about the product, it’s about understanding what lies beneath the skin and how it functions.

Final Thoughts

Successful outcomes rely on more than product placement. They demand anatomical understanding, clinical sensitivity, and a respect for each patient’s unique facial dynamics. In short, the best Botox treatments don’t freeze the face – they refine it.