Botox forehead lines: why treat them, and how?

The forehead is one of the eleven areas of our atlas of botulinum toxin treatment areas. This page explains which muscle is involved, what the toxin can and cannot do in this area, which toxins are approved, and with what onset, duration and risks. It does not replace a consultation.

Why are forehead lines treated?

Forehead lines are horizontal creases that appear when you raise your eyebrows, for example to show surprise. They are caused by the contraction of the frontalis, a broad sheet of muscle under the skin of the forehead, which pulls the eyebrows upwards. After repeated contractions, these creases can remain visible at rest.

Botulinum toxin temporarily relaxes the frontalis: it contracts less, and the creases deepen less when you raise your eyebrows. The labels describe injection into this muscle at several points lined up horizontally, away from the eyebrow and the rim of the eye socket^1,2. The effect is temporary.

What the toxin does not do: it does not act on skin quality or on a forehead that has sagged with age, and it does not erase a deep crease at rest in the same way as a crease that forms with movement. The vertical creases between the eyebrows belong to another area, covered on the page about treating frown lines; the labels also describe treating both areas at the same session¹.

When is the toxin used?

The labels covering this area concern moderate to severe forehead lines seen when the eyebrows are raised as far as possible, when their severity has an important psychological impact, in adults^1,2. How much the lines bother you is therefore part of the indication.

The labels contraindicate injection in case of allergy to the toxin or to a component of the product, a generalised disorder of the muscles and of the junction between nerve and muscle (myasthenia gravis, Lambert-Eaton syndrome), or an infection at the injection site^1,2. Treatment is not recommended during pregnancy or breastfeeding¹.

Which toxin for forehead lines?

Depending on the product: not every type A toxin approved for aesthetic use covers this area.

The forehead is approved for some type A toxins only: not all the toxins with an aesthetic indication in France cover this area^1,2,4. Your doctor chooses the product with these indications in mind.

The short-acting botulinum toxin (serotype E) is approved for frown lines only, in the European Union and in Canada: the forehead is not part of its marketing authorisation^3,5. Using it in this area would be off-label and has not been evaluated in the trials that led to its approval³.

Is it right for me?

This is a decision to make with your doctor. They will look at how your forehead moves, the height of your eyebrows, the appearance of your eyelids, and whether the lines persist at rest. They will take into account your medical history, your treatments, any pregnancy plans, and your expectations: a forehead that keeps some movement, or a more marked relaxation.

Age matters too. Trial data are limited after 65 for one of the toxins approved for the forehead¹, and another is indicated only in adults under 65².

Questions to ask your doctor: should frown lines be treated too? What is the risk of a drooping eyebrow in my case? How long should the effect last? What happens if the result is uneven?

Onset and duration

For the type A toxins approved for the forehead, improvement usually appears within a week of the injection^1,2. The peak effect is seen around day 30 according to one of the labels². The effect has been shown for about 4 months^1,2, and a reduction in forehead line severity was observed for up to 6 months in one study¹. Sessions are at least 3 months apart^1,2.

These timelines are explained in more detail on the page about how long botulinum toxin takes to work.

What are the risks in this area?

For forehead treatment, one label lists as common: drooping of the upper eyelid (median onset of 9 days), drooping of the eyebrow (median onset of 5 days), the Mephisto sign (eyebrow arched upwards at its outer end), headaches and small bruises at the injection site¹. Another label also describes a feeling of heaviness in the forehead and facial asymmetry². These effects are temporary and disappear as the toxin wears off.

The drooping eyebrow has a simple explanation: the frontalis is the muscle that lifts the eyebrows, and relaxing it can let them drop. This is why eyebrow position is assessed before the injection, and why the page on the eyebrow lift and the one on crow’s feet complement this one.

As with any botulinum toxin injection, difficulty swallowing, speaking or breathing requires immediate medical attention^1,2. A visual disturbance should also be checked by a doctor promptly. If something unexpected happens, the page on what to do after a forehead injection helps you recognise it.