Your forehead may be working to keep your eyes open.

Sometimes, and predictably. Toxin weakens the only muscle that lifts the brows; if that muscle was doing a job — holding hooded lids or fallen brows out of your eyes — the forehead goes smooth and the face goes heavy for three to four months. The trials, which select patients with adequate brows, put brow droop at about 2% and eyelid droop at 2% against 0% on placebo. Do the eyelid test before booking: close, relax, open slowly without raising. If the lids hood, ask for the frown lines only or a light dose high on the forehead, or treat the lid or brow instead. If they do not, standard dosing above the convergence line is safe in experienced hands. Photograph the brow first, either way.

Toxin removes the movement, not the print. A line present at rest has creased the collagen beneath it, and the first treatment will soften it and stop it deepening rather than erase it; with the muscle quiet across two or three cycles most etched forehead lines shallow noticeably as the skin stops being folded. The residue is a skin problem: a retinoid for the fine ones, a soft superficial gel threaded under the deep ones (83% improved at 12 weeks in the post-market study behind its European indication), fractional resurfacing for the deepest. In a thick, flattened male forehead, structural support on the bone is sometimes what makes the furrows stop folding at all.

The frontalis and the frown complex are a tug of war. Weaken the frontalis alone and the corrugators and procerus pull the brows down unopposed — the mechanism of a dropped brow; weaken the frown muscles as well and the lifter needs less force, which is why forehead lines improved from grade 3.0 to 1.0 over three cycles in an 18-person pilot that treated the glabella only. The pivotal forehead trials and the licence both pair 20 units in the forehead with 20 in the glabella for this reason, and the label's brow-droop rate of 2% comes from that pairing. An injector who offers forehead-only treatment is offering a heavier brow.

The frontalis on each side works for its own eye. When one upper lid sits lower or hoods more, that side's forehead lifts all day and prints its lines, while the other rests. In the 160-patient series every one of the 28 patients with one-sided fixed forehead lines had eyelid ptosis on the same side. Look at a straight-on photograph: the lined side will show less upper lid and a lower brow. Toxin on that side evens the forehead and drops the brow that was already low; the fix is the lid, and a one-sided ptosis is worth an oculoplastic opinion, because some causes are medical rather than cosmetic.

Safe in the trials that reported it — no vascular events in the 132-patient forehead-contour trial, mild reactions in the 18-month superficial-gel study — and dangerous in the wrong hands, because the forehead's arteries connect to the eye. The consensus on visual loss names the forehead, glabella and nose as the sites of greatest risk, and 511 cases of filler blindness have been published. The precautions are specific: superficial placement for lines or on the bone for contour, a cannula, aliquots of a tenth of a millilitre or less, slow injection, hyaluronidase in the room and a clinician who knows the protocol. For most foreheads, toxin plus a retinoid gets there without the risk; filler is for the etched line that remains.

It depends on what the frontalis is doing. A forehead that relaxes without hooding is a toxin forehead: two phase 3 trials and a licence. A forehead that hoods when it relaxes is a working forehead, and the question is what it is holding up: if the lids carry excess skin and the brows sit at a reasonable height, upper blepharoplasty lets the frontalis stand down — its electrical activity halved at a year with skin-only surgery in a randomised trial; if the brows themselves have fallen, a brow lift — about 2 mm for a year with focused ultrasound, 3–4 mm for years endoscopically — is the treatment, and a blepharoplasty alone would drop them further. Over sixty, most working foreheads have both, and surgeons plan the lid with a browpexy or a lift. Toxin can be added lightly afterward for what movement remains.

Effect at a week, peak at two, and three to four months of a quiet forehead for the licensed products, with the movement returning gradually rather than overnight. Intradermal micro-dosing wears off sooner. The long-acting daxibotulinumtoxinA has phase 2 forehead data and a glabellar licence with longer median duration. The useful pattern is that etched lines shallow across successive cycles as the skin stops being folded, so the second and third treatments often look better than the first even at the same dose; and the useful discipline is to let the muscle come most of the way back before the next dose, so the brow's resting height can be checked each time.

Forehead lines are the earliest dynamic lines, and prevention is about how often the skin is folded and how well it springs back. Sunscreen every morning and a hat outdoors keep the recoil; a retinoid from the late twenties rebuilds it; sunglasses and a current prescription stop the brows lifting to see; and noticing the habit of talking with the eyebrows is free. When a line begins to stay a moment after the raise, a light toxin dose with the glabella keeps the fold from printing, with the strongest evidence on this page behind it. Filler and resurfacing are for lines that exist; the 30s guide covers the decade.

Toxin softens the forehead within a week and peaks at two, which is when brow height is compared with the photograph and the dose adjusted for next time. A superficial filler shows immediately and is judged once swelling clears at two weeks. Retinoids change the surface over eight to twelve weeks. Focused ultrasound lifts the brow over 90 days as collagen forms. Fractional resurfacing is pink for a week or two and judged at three months. Blepharoplasty and a brow lift are bruised for two weeks, presentable at a month and final at six, with scalp numbness after a brow lift lasting months. Photograph straight on, at rest and raised, before anything.

The ladder in euros: sunscreen, a hat and a retinoid (€20–60 a month, the skin half) → an eye test and sunglasses (free, the habit half) → toxin with the frown lines (€150–350 every three to four months, the strongest evidence on the page) → a superficial filler for etched lines (€300–600, six to twelve months, with the arterial caveat) → fractional resurfacing (€400–1,500) → an ultrasound brow lift for the low brow (€400–800 a year) → upper blepharoplasty when the lids are the cause (€2,500–5,000, once) → an endoscopic brow lift when the brows have fallen (€5,000–8,000, once). Patches, peptides and gadgets sit outside the ladder for this problem.

Two different droops. Brow ptosis is the frontalis weakened past what the face can spare: the brows sit lower, the lids look hooded, the face reads tired, for three to four months; the prescribing information puts it at 2% in the pivotal trials, and eyelid ptosis — toxin reaching the muscle that lifts the lid itself — at 2% against 0% on placebo, with headache in 9% against 5% (prescribing information). Trial patients are selected for adequate brows; in the clinic the incidence follows the patient, and the reviews name the causes plainly — wrong site, too much dose, and the wrong forehead (complications review). The prevention is anatomy: small doses spread high across the forehead above the convergence line, nothing within a centimetre of the brow, the sides treated so the lateral frontalis does not peak into a "Spock" brow, and the glabella treated so the lifters have less to fight (convergence-line study; 2025 review). An eyedrop can lift a drooping eyelid a little for the duration; nothing lifts a dropped brow except time. Photograph the brow before, review at two weeks, and take a heavy result as information for the next dose, not a reason for more.

The supratrochlear and supraorbital arteries climb the forehead from the orbit, and filler forced into either can travel backward into the ophthalmic artery and occlude the retina. The consensus on minimising embolic visual loss names the forehead, glabella and nasal dorsum as the locations of greatest risk (consensus), and the 2024 review counts 511 published cases of filler-related blindness worldwide, the majority from these central sites (2024 review). The safeguards are the ones the trials used: superficial placement for lines or supraperiosteal for contour, a blunt cannula, aliquots of a tenth of a millilitre or less, slow injection with aspiration, no forehead filler after recent toxin has changed the landmarks, hyaluronidase in the room, and an injector who knows the emergency protocol by heart. Sudden pain, blanching or any change in vision during or after treatment is an emergency in minutes. The filler guide covers it.

The frontal branch of the facial nerve — the one that moves the forehead — crosses the temple just under the skin on its way to the frontalis, exactly where brow-lift ultrasound passes are placed; a weak brow for weeks is the recognised risk, sometimes with patches of numbness from the sensory nerves nearby, and the 42-person blinded study reported none (blinded brow study). Ultrasound is painful for minutes and can melt superficial fat in a temple that has none to spare. Radiofrequency microneedling on the forehead burns if the depth or energy is wrong, and the FDA's alert on burns and scarring is recent (FDA alert). Ask who holds the handpiece and how many foreheads a month.

The endoscopic brow lift's costs are the scalp's: numbness and itching for months where the sensory nerves were stretched, small patches of hair loss at the incisions, and the lateral brow relapsing 2–3 mm in some series within six months (meta-analysis). The blepharoplasty's paradox is the brow: removing lid skin lets the frontalis relax, and the brow descends 1–4 mm — welcome in a brow that was being held too high, unwelcome in one that was already low. In 93 patients having upper-lid surgery for ptosis, the brow came down by at least 5% in 61%, more often in men and with larger skin excisions (case-control study); an internal browpexy or a combined brow lift is planned when the brows start low (browpexy study). Dry eye and incomplete closure follow an over-resected lid. A surgeon who assesses the brow before the lid is the one to choose.