Botulinum toxin doesn’t erase a wrinkle. It temporarily weakens one specific muscle, and the line that softens is whichever line that muscle was folding, so the anatomy decides the outcome, not the number of units on the invoice. The frontalis makes horizontal forehead lines. The corrugators and procerus make the vertical elevens. The orbicularis oculi makes crow’s feet. The masseter isn’t a wrinkle muscle at all; treating it changes jaw width. Dose follows the bulk and strength of the muscle, which is why a masseter takes several times what a chin does. It’s a prescription medication, and the person holding the syringe should be a board-certified injector who maps how your face moves before touching it.
Dynamic lines move. Static lines don’t.
Pull a straight face in good light and look. Creases that vanish when you stop moving are dynamic lines, and those are what a neurotoxin addresses, because a relaxed muscle stops folding the skin. Anything still visible at rest is a static line: a crease folded so many times the dermis has remodeled around it.
Research suggests a quieted muscle can let a shallow static line soften over repeated treatments. A deep, permanent groove is a different problem. Filling it, resurfacing it or stimulating collagen in it are separate conversations, usually layered on top of the toxin, and the full menu of what pairs with what lives in the full injectables guide. An injector who promises a resting forehead line will vanish on toxin alone is overselling.
The forehead is one sheet, and it’s the only thing lifting your brows
The frontalis is a broad fan running from the hairline down into the brow. Raise your eyebrows and it contracts, bunching the skin into horizontal bands. It’s also the only elevator of the eyebrow in the entire face.
Shut it down without dealing with the muscles pulling downward and the brow falls to wherever the depressors want it. The lid feels heavy and the eye looks hooded. Injectors generally treat it lightly, keep a margin above the brow, and treat the glabella in the same session so the downward pull comes off too.
Relax the central fibers and leave the outer ones alone, and the tail of the brow keeps lifting while the middle stays put. That peaked look is the Spock brow. It’s usually correctable with a small touch-up and wears off on its own. If your brows already sit low, or you hold your forehead up all day to fight heavy lids, a conservative dose or none at all is the safer call.
The elevens are three muscles working together
The vertical lines between the brows come from a cluster: the corrugators pulling the brows inward, the procerus pulling the inner brow down at the root of the nose, and the depressor supercilii adding to the drag. It’s the complex that fires while you squint at a spreadsheet, and it’s strong, so the dose here usually runs higher than anywhere else in the upper face.
Since these muscles pull the brow down, quieting them lets the untouched frontalis win and the brow can drift up a millimeter or two. That’s the so-called chemical brow lift, which is just an opposing force removed.
The complication here is true eyelid ptosis: the upper lid itself dropping, when product spreads to the muscle that holds the lid open. It’s uncommon and temporary, and prescription drops can partly compensate while it wears off. Brow heaviness is a different mechanism (too much forehead, no lid involvement) with a different fix.
Crow’s feet, and the lines around the eye a neurotoxin shouldn’t chase
The orbicularis oculi is the ring muscle that closes the eye, and its outer fibers fan the skin into crow’s feet when you smile or squint. Treatment here sits shallow and outside the bony rim of the eye socket, in small amounts, because the skin is thin and the muscle sits close to the surface.
Too low and too far forward on the cheek, and the toxin can reach the muscle that lifts the corner of the mouth, leaving an uneven smile for as long as it lasts. Weaken the lower ring in someone whose lid is already lax and you can get dry eye or a puffier under-eye.
Below the cheekbones, the margin for error shrinks
Lower-face work means smaller doses and far less forgiveness, because these muscles run your mouth. The depressor anguli oris drags the mouth corner down, feeding the tired expression and the marionette shadow. Placed too close to the center, the toxin catches the lower-lip muscle instead: a crooked smile, trouble with a straw, an odd feeling when you speak.
The mentalis creates the pebbled, orange-peel chin when it’s overactive, and a small amount low on the chin usually smooths it. Too high, and pursing your lips gets harder. The platysma is the sheet across the neck behind those vertical bands, and easing its downward pull can sharpen the jawline a little. Too much, or too deep, has been reported to cause neck weakness and trouble swallowing.
The masseter isn’t a wrinkle treatment at all
The masseter is the chewing muscle you feel at the back of the jaw when you clench. It’s treated to ease clenching and grinding and to narrow a jaw that’s wide because the muscle itself is enlarged.
Relief from clenching comes first; any contour change takes weeks to months and needs repeat sessions to hold. Side effects scale with the muscle: chewing fatigue, a temporary smile change if product spreads. If grinding is your reason, get a dental evaluation too, since the toxin quiets the muscle without addressing why you clench.
Units are the wrong number to ask about
A glabellar complex takes more than the fine ring around the eye. Unit counts also aren’t portable between products, since potency is measured differently for each. How the brands stack up is its own post: our head-to-head of Botox vs Jeuveau vs Dysport covers it.
| Muscle | What it does — and what misplacement looks like |
|---|---|
| Frontalis | Horizontal forehead lines; the only brow elevator. Over-treated: heavy brow and hooded lids. Uneven across the sheet: peaked Spock brow. |
| Corrugators + procerus | The vertical elevens. Relaxing them can raise the brow slightly. Deep or low placement risks true eyelid ptosis. |
| Orbicularis oculi | Crow’s feet. Too low or too medial reaches the smile muscles; too much in the lower ring means dry eye and puffiness. |
| Depressor anguli oris | Pulls the mouth corner down. Misplaced medially, the lower lip stops moving evenly and the smile goes crooked. |
| Mentalis | Chin pebbling. Placed too high, the lips become hard to purse or close firmly. |
| Platysma | Vertical neck bands and downward pull on the jawline. Excessive or deep dosing has been linked to neck weakness and swallowing trouble. |
| Masseter | Clenching and jaw width, not wrinkles. Large muscle, large dose, slow result, chewing fatigue as the common complaint. |
The risks nobody puts on the price list
Bruising and a day or two of headache are the everyday risks. The placement problems above share a pattern: they’re temporary, fade over three to four months, and are far likelier when the injector works fast, cheap, or without watching your face move. Prescribing information for these products also warns about effects spreading beyond the injection site. If you’re pregnant or breastfeeding, or have a neuromuscular condition such as myasthenia gravis, treat this as off the table until a physician says otherwise.
This is a prescription drug given by injection. A board-certified dermatologist, plastic surgeon, or a licensed injector under real physician supervision is the standard. Ask who holds the syringe and what happens if something drops. The hours afterward are covered in our guide to injectable aftercare, and starting before any lines show at rest gets its own answer in our piece on preventative Botox.
What helps the lines a neurotoxin can’t reach
None of these substitutes for an injectable. They work on the static half of the problem: collagen, sun damage, sleep creasing. Affiliate links below.
La Roche-Posay Anthelios Sunscreen
Sun damage is what turns a moving line into a permanent one, so daily SPF is the highest-leverage thing here
Retinol Serum
The best-studied over-the-counter option for collagen, the layer a static crease lives in
Vitamin C Serum
Antioxidant backup under sunscreen, plus a modest brightening effect
Silicone Wrinkle Patches
Hold the skin flat overnight, worth trying if your creases are worst on the side you sleep on
Night Guard for Grinding
Protects the teeth a masseter treatment doesn’t; the muscle gets quieter, the habit stays
Prices move constantly, so we link to live listings instead of printing a number that is wrong by the time you read it. Links go to Amazon, which is where a referral gets credited.
More of our treatment coverage sits in the skin archive.
If I Were You
If your brows sit low or your lids already feel heavy, ask for the glabella alone on the first round and leave the forehead untreated, because the frontalis is the only muscle holding your brows up.
If your forehead lines still show in a straight-faced photo, plan on resurfacing or a collagen treatment alongside the toxin, because a static crease is remodeled skin that a quiet muscle can’t unfold.
If you have jaw pain and worn-down molars from clenching, see a dentist before booking masseter injections, because a night guard protects the teeth and the toxin only softens the force behind the grinding.
If a previous session left your brow heavy or your lid dropped, go back with photos and name which one it is, because the two have different causes and the fix for one can worsen the other.
If your smile went uneven after lower-face work, tell your injector and wait it out rather than adding product to chase symmetry, because it fades on its own and more toxin in a compensating muscle can turn a small asymmetry into a large one.
Common questions
Does more Botox mean a better result?
No. Past the amount needed to quiet a given muscle, extra product mostly buys stiffness and a higher chance of spread.
How long before I can tell if the placement was right?
Onset starts within a few days and the full effect settles around two weeks, so providers generally ask you to wait fourteen days before judging it or asking for a touch-up.
Can it fix lines I have when my face is completely still?
Only partly, and slowly. Relaxing the muscle stops the line deepening and can let a shallow one soften over repeat treatments, but a deep groove needs something that works on the skin itself. Ask whether resurfacing, microneedling or filler belongs in the plan.
Is it safe to get at a med spa?
That depends on who injects and who supervises them, which varies by state. Ask about credentials and who handles complications. A board-certified dermatologist or plastic surgeon is the conservative choice, especially for lower-face work.
Ask about the map, not the number
A good consult ends with someone naming the muscles they plan to treat and what each will change. A bad one opens with a price per unit. Placement is the skill you’re paying for; the vial is the same in every clinic in town.
