Forehead lines and crow's feet: one question decides everything
Published 25 September 2026 · Reviewed by Dr Sin Yong
Look in a mirror with a neutral face. Are the lines there — or do they only appear when you raise your brows and smile? That single observation sorts upper-face lines into two different problems with two different treatments, and explains most of the disappointment in this field: dynamic lines respond beautifully to muscle relaxation, while lines already etched at rest need the skin itself repaired. Knowing which you have before treating is the whole game.
Lines are graded at rest and in motion — the gap between the two states writes the plan.
Key facts
Dynamic lines
Lines that appear only during expression — brow raise, frown, smile — and vanish at rest
Static lines
Lines visible with the face fully at rest — the crease has become a structural fold in the skin
Frontalis
The brow-lifting muscle whose repeated contraction pleats the forehead horizontally
Orbicularis oculi
The eye-closing muscle whose lateral fibres fan the crow's feet on smiling
BTX mechanism
Temporarily reduces the muscle contraction that folds the skin — the dynamic-line treatment
Skin remodelling
Lasers, microneedling RF and biostimulation rebuild dermal collagen — the static-line territory
Progression
Dynamic lines left folding for years gradually etch into static ones — the case for timely treatment
How a moving line becomes a permanent one
Every brow raise pleats the forehead skin; every genuine smile fans the skin beside the eyes. In young skin, rich in collagen and elastin, the pleats spring back the moment the muscle relaxes. With years of repetition — hundreds of contractions a day, in Singapore sun that quietly degrades the spring — the skin begins to hold the crease, first faintly at rest, then unmistakably. A dynamic line is a fold the skin still recovers from; a static line is a fold the skin has learned. The Carruthers' foundational trials showed how reliably relaxing the muscle smooths the former; nothing about relaxing a muscle un-learns the latter.
“If the line is there at rest, relaxing the muscle will not remove it. The skin has learned the crease — and the skin is what needs treating.”
Dr Sin YongOn the dynamic–static distinction
Treating dynamic lines
For lines that live in expression, reducing the excess contraction is the direct answer: precise doses into the frontalis for horizontal forehead lines, the glabellar complex for frown lines, the lateral orbicularis for crow's feet. Modern dosing aims for softened movement, not paralysis — you should still look interested, surprised and amused, just without the deep pleating. The forehead deserves particular respect: the frontalis is also the brow's lifter, and overdosing it drops the brows into heaviness. Conservative first sessions with a two-week review beat heroic ones.
Treating static lines
A line present at rest is a dermal problem, and dermal problems need dermal treatment: fractional laser resurfacing and microneedling radiofrequency to remodel collagen in the creased skin, biostimulatory skin treatment to thicken its support, and occasionally a whisper of filler in a deeply etched individual line. Muscle relaxation still helps here — it stops the etching from deepening while the skin work proceeds — but expecting BTX alone to erase an etched crease is the commonest disappointment in upper-face treatment, and an honest clinic says so before the first injection.
Crow's feet: the friendly lines
A note in defence of the eye corners: crow's feet are the most socially forgiven lines on the face — they read as warmth, and their complete absence during a broad smile reads as something subtly wrong. Treatment here aims to lighten the fan, not delete it. The distinction matters most in Asian skin, where the lower crow's feet fibres also contribute to the cheek's smile shape; heavy lateral dosing can flatten a smile in a way no one asked for. Light hands, reviewed results.
Almost always because the lines were static — etched into the skin at rest — before treatment. Muscle relaxation stops the folding but cannot repair the crease the skin has learned; that needs skin-remodelling treatment. This is the most important expectation to set in upper-face work.
A reasonable trigger is the transition point: when lines that used to vanish at rest start faintly persisting. Treating around that stage keeps dynamic lines from etching in. Starting earlier is a personal choice; starting much later just means the plan includes skin repair as well as relaxation.
Not with contemporary dosing, which targets excess contraction rather than all movement. The forehead is dosed to soften pleating while preserving brow lift; the eye corners are dosed to lighten the fan while keeping the smile. A two-week review lets the dose be trimmed to your face rather than a template.
Dermal remodelling: fractional lasers, microneedling radiofrequency and collagen-biostimulating treatment rebuild the creased skin over a series of sessions, usually with muscle relaxation alongside to stop further etching. Deeply etched single lines occasionally take a small amount of filler.
Months, with gradual complete wear-off; most patients settle into treatment two to three times a year. Duration varies with dose, muscle strength and individual metabolism — your pattern becomes predictable after a session or two.
Worth lightening, rarely worth erasing. Eye-corner lines read as warmth, and a completely smooth lateral eye during a big smile looks subtly artificial. Good treatment reduces the depth of the fan while leaving the smile intact.
Substantially. Ultraviolet degrades the collagen and elastin that let skin recover from folding — it accelerates the dynamic-to-static transition. Daily sunscreen is genuinely part of line treatment in Singapore, not an optional extra.
Forehead lines are horizontal, made by the brow-raising frontalis. Frown lines are the vertical '11s' between the brows, made by the glabellar complex. They are assessed and dosed separately — and the balance between them matters, because the same muscles also position your brows.
References
Carruthers JA, Lowe NJ, Menter MA, et al. A multicenter, double-blind, randomized, placebo-controlled study of the efficacy and safety of botulinum toxin type A in the treatment of glabellar lines. J Am Acad Dermatol 2002;46(6):840–849. source
