In short. A muscle-relaxing injectable in the frontalis: why the whole muscle is rarely the target, what is measured before treating, and how the brow position is judged in advance.

Key points

  • Reducing the pull of a brow-lifting muscle lowers the brow.
  • How much that matters depends on where the brow sits when the muscle is not working, how much of the upper lid it is holding clear, and whether the two sides match.

Botulinum toxin of the A type is the rung that reaches the mechanism of a horizontal line. Its effect on the line is the clearest on the ladder, and its trade is the largest, because the muscle it quiets is the only one that lifts the brow.

What the category does

The toxin reduces the signal reaching the muscle from the nerve ending that supplies it, so the muscle contracts less and the skin it was gathering is no longer folded. It is a temporary reduction in movement rather than damage to the muscle, and it does not touch a crease that has settled into the skin.

Why the whole muscle is rarely the target

The frontalis is a broad sheet, and the lines across a forehead are usually made by one part of it working harder than another. A plan therefore concerns which parts are treated and in what proportion rather than how much is used. The aim in most faces is to soften the folding while leaving enough lift for the brow to sit where it belongs.

The trade, and how it is judged

Reducing the pull of a brow-lifting muscle lowers the brow. How much that matters depends on where the brow sits when the muscle is not working, how much of the upper lid it is holding clear, and whether the two sides match.

What is measured before it is given

Brow height at rest, and again with the frontalis deliberately relaxed. The position of the upper lid. The pattern of the folds at full contraction, including any difference between the sides, and any previous treatment with its timing. The reasons the muscle is active are identified here too.

What the weeks afterwards look like

The effect arrives over several days rather than at once. A brow that feels heavy, an upper lid that looks lower, or a forehead that feels tight are the changes people most often report, and they are usually the trade being felt rather than a complication.

How often it is repeated

Movement returns as the effect wears off, commonly over months rather than weeks, and the interval differs between individuals and between treatments in the same person. Each repeat is a fresh decision rather than a standing order. On this muscle, holding the effect at its peak keeps the brow lower for all of that time.

Reasons to seek advice rather than wait

  • Difficulty swallowing, speaking or breathing, double vision, or weakness spreading beyond the face needs emergency care.
  • An upper lid that droops and does not settle, or an eye that becomes persistently dry or irritated, needs review by the treating team.
  • A forehead treated without anyone recording brow height and lid position first, which leaves the trade unmeasured.

Why relaxing this muscle changes the brow is set out in reading the lines and the brow together. What is recorded at the consultation is described in how a clinician assesses the forehead, and where repetition stops adding anything is covered in the honest ceiling.

Related reading

Frequently asked questions

Why not relax the whole frontalis and be finished with the lines?

Because the frontalis is the muscle that holds the brow up, and a forehead with no movement at all has no lift left in it. The lines across a forehead are usually made by one part of a broad sheet working harder than another, so a plan concerns which parts are treated and in what proportion. Softening the folding while leaving enough lift for the brow is the aim in most faces.

If my brow sits lower afterwards, how long does it stay there?

As long as the effect lasts, which is months rather than weeks, and then the muscle recovers and the brow returns to the position it held before. Nothing about it is permanent in either direction. That is why the position is recorded before treatment rather than compared afterwards: the change is one a person lives with for a season, not one that passes in a few days.

What does a heavy feeling across the brow in the days after treatment mean?

It is usually the trade being felt rather than a complication: the muscle that was lifting the brow is pulling less, and the weight of the brow is carried by the tissue underneath instead. It commonly settles as the effect settles. If the upper lid itself droops, or an eye becomes persistently dry or irritated, that is worth reporting to the treating team rather than waiting out.

Risks & Limitations

  • Relaxing the frontalis also lowers the brow, because the same contraction holds it up. How far it drops is judged before treatment, not discovered afterwards.
  • A line that is still visible with the face at rest has a component in the skin, and no treatment directed at the muscle removes it.
  • The relaxing effect wears off and the treatment is repeated, so the appointments do not end on their own.
  • Resurfacing brings real downtime and a risk of pigment change that is higher in skin which tans easily.
  • Volume placed into a crease rather than into a hollow can show as a ridge under light, and it does not remove the line.

When to Seek Care

  • A brow that has dropped on one side only, or that can no longer be lifted on one side.
  • A forehead that has stopped moving, or sudden weakness, difficulty speaking or swallowing, or double vision, which need emergency care rather than a routine appointment.
  • A new lump or swelling over the brow or the upper forehead, or a spot that bleeds, crusts or fails to heal.
  • Severe pain, or skin that turns white, dusky or mottled, after an injection in this area. Any change in vision afterwards is an emergency.
  • A drooping upper lid, or an eye that becomes persistently dry or irritated, after treatment to the forehead.

References & Further Reading

  • American Society of Plastic Surgeons (ASPS) — procedure and safety guidance
  • National Institute for Health and Care Excellence (NICE, UK) — relevant guidance
  • Cochrane Library — systematic reviews
  • Chinese Medical Association Plastic Surgery Branch — clinical guidance

Medically reviewed by Ke He, MD (何锞), Deputy Director & Head of Skin & Laser Aesthetics. Last reviewed: 19 September 2026.

This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.