The research rarely sets the two against each other. In a 2021 Cochrane review of the toxin for facial wrinkles, a placebo was the comparison in 36 of 65 randomised trials. A small number compared the toxin with fillers. The review lists comparisons with other treatments among the gaps in the evidence. So this article does not rank them. It sets them side by side, explains how a doctor tells movement from lost volume, and lists the risks of each.
What botulinum toxin does to a line, and what a filler does instead
Botulinum toxin works on the muscle under a line. Injected into chosen muscles, it turns down how strongly they contract. A muscle that contracts less pulls less on the skin above it, so a line made by that movement creases less. A 2016 global consensus on the toxin, written by plastic surgeons and dermatologists from several countries, describes a shift toward “neuromodulation rather than paralysis”. That means turning a muscle down rather than switching it off. Dr Samantha describes the aim of a dose this way.
“It's about giving enough to reduce muscle movement so that it doesn't pull on the skin that the dynamic lines show and deepen with time, but yet still being able to make expressions and not look frozen.” Dr Samantha Tay
A filler works on shape rather than on a muscle. It is placed under the skin to replace volume in a hollow or a fold, or to build a contour such as the chin. Dr Samantha has described its job in a video about fillers and skin boosters.
“Fillers are meant for volumizing, so you fill up, like, areas with volume defect for facial augmentation, like to have a sharper chin, more prominent cheeks, so they can shape and define your features.” Dr Samantha Tay
Hyaluronic acid is the type tested in the filler trials cited here; poly-L-lactic acid and calcium hydroxylapatite are other types. Our pages on anti-wrinkle injections and dermal filler treatment describe both treatments at Nexus.
How a doctor tells whether a line comes from movement or lost volume
Lines that appear when you frown, raise your brows or smile are called dynamic lines, because they come and go with movement. With time the same creases can stay in the skin when the face is still, and these are called static lines. A hollow or a fold is something else: a change in shape where volume under the skin has been lost.
That difference decides the treatment. The 2016 consensus on the toxin puts it in two sentences. “Muscles are targeted where their excessive contraction is the primary cause of the changes that are seen. Volume is restored where this is the primary cause.” It also asks doctors to look at each muscle together with the tissues around it. It is expert opinion rather than a trial, and the meeting behind it was supported by a manufacturer.
You can get a rough idea in a mirror. Frown, then relax, and watch whether the line fades. A line that fades points to movement; a line that stays may involve lost volume, the skin itself, or both. A mirror cannot show what lies under the skin, which is what a doctor's examination is for. Dr Samantha spoke about static lines in a 2023 video.
“Treating static lines is relatively more inconvenient and sometimes can't totally be eliminated.” Dr Samantha Tay
Which parts of the face usually get botulinum toxin, filler or both
Where each one goes follows the cause. The toxin trials concentrate on the upper face. In the Cochrane review, 43 of 65 trials treated the frown area between the brows. Smaller numbers treated crow's feet, the forehead and the area around the mouth. The 2016 consensus describes the toxin's use spreading from the upper face to the lower face, the neck and the midface.
Fillers go where volume is missing or a contour is being built. Dr Samantha's description above names the chin and the cheeks. A hollow, such as the one under the eye, is another place filler is used, and the lips are one more. Each area takes a filler of its own firmness: a softer gel for the lips and under the eye, and a firmer one for the chin and the jaw.
Some areas can involve a muscle and a shape at once. The jaw is one example. Our page on face slimming looks at the causes behind a wide lower face, from the chewing muscle to fat and skin.
How long anti-wrinkle injections and fillers are reported to last
For the toxin, the figures come from frown lines. An analysis of four pooled trials, published in 2012, looked at 621 people treated with one product. Among the people who responded, the effect lasted a median of 120 days for lines when frowning and 131 days for lines at rest. The authors summarise it as a benefit lasting 4 months in more than 50% of responders.
Those figures are for one product on frown lines. For the forehead and crow's feet, Nexus gives the toxin's effect as 3 to 4 months, and for the chewing muscle of the jaw, 4 to 6 months.
For fillers, the studies used here give no general figure. At Nexus, hyaluronic acid filler is given as lasting about 6 to 18 months, depending on the area and the product. The lips, which move all day, sit at the shorter end.
Either way, keeping the effect means repeat treatment. A review visit is where the doctor looks at how the area has settled and decides whether anything more is needed. At Nexus, a toxin session is followed by a review two weeks later, and whether a top-up is needed is decided there. After filler, a photo review is planned two to four weeks later.
Which can be reversed if something goes wrong, botulinum toxin or a filler
A 2024 review of the enzyme hyaluronidase states that it can reverse complications of hyaluronic acid fillers. The same review notes that controlled data are limited, while clinical experience with it is growing.
The enzyme breaks down hyaluronic acid filler. The review names fillers the enzyme cannot dissolve, such as poly-L-lactic acid and calcium hydroxylapatite, so ask which type of filler is planned. Botulinum toxin has no equivalent reversing step. Its effect wears off with time, as the figures in the section above show.
What the risks of botulinum toxin and fillers look like in the trials
Both treatments carry risks, so here they are side by side, as the studies report them. For the toxin, a 2016 meta-analysis of 16 placebo-controlled trials found more adverse events in the toxin groups than with placebo. Headache, eyelid ptosis (a drooping upper eyelid) and heavy eyelids were reported more often after treatment of frown lines. After treatment of crow's feet, the one significant increase was a bruise, or haematoma, at the injection site. The authors describe these effects as mild to moderate.
On ptosis, the Cochrane review points the same way. It found that the toxin probably increases the risk of eyelid ptosis. The major adverse events reported were mainly ptosis. The toxin is also known to carry a risk of a squint or a change in eyelid sensation.
For hyaluronic acid fillers, a 2024 systematic review of 48 randomised trials looked at adverse events. They were mostly short-lived reactions at the injection site that settled on their own. Severe adverse events were rare, but they lasted for months and needed active medical treatment.
The gravest filler risk is a blocked blood vessel. A 2015 review of the world literature found 98 reported cases of vision change after filler. A person's own fat, used as a filler, was involved in 47.9% of them and hyaluronic acid in 23.5%. Pain and loss of vision were the commonest symptoms, and in the majority of cases the loss of vision did not recover. The authors call the risk of blindness from fillers rare. They also say the injecting doctor needs a firm knowledge of the blood vessels of the face.
So after a filler injection, severe pain or any change in your sight needs attention straight away. Contact the clinic, or go to an emergency department. The hyaluronidase review describes a blocked vessel and loss of vision as emergencies that need high-dose treatment without delay.
Why doctors often use botulinum toxin and a filler together
Many faces show both lines from muscle movement and areas of lost volume, so the two are often used together. A 2016 global consensus on combining hyaluronic acid fillers with the toxin states that “combined treatment is now a standard of care”. It also recommends lower toxin doses, to turn muscles down rather than switch them off, where lost volume affects how a muscle works.
The consensus is expert opinion rather than a trial. As with the consensus on the toxin, the meeting behind it was supported by a manufacturer.
Whether both are done at one visit, and in what order, is decided at the consultation.
Neither injection covers every concern. For deep lines at rest, a skin booster or microneedling radiofrequency may be added. Loose skin is a different concern: high-intensity focused ultrasound suits loose skin along the jaw, radiofrequency suits loose skin in the mid-face and fine surface lines, and severe sagging is referred to a plastic surgeon. Choosing no treatment is an option too. Our non-surgical face lift page explains how these fit together when more than one layer of the face is involved.
Why the research does not rank one treatment above the other
If you searched for which one is better, the honest answer is that the studies do not say. Each treatment acts on a different cause. The Cochrane review found a small number of studies comparing the toxin with fillers. None of the papers used for this article ranks one above the other. What the 2016 consensus on the toxin supports is matching the treatment to the cause.
Here are the two side by side, with the same questions put to each.
What to ask the doctor before you choose either treatment
The choice is made at a consultation, after the doctor has examined you. The questions below help you leave with a clear idea of what is causing the change you see. They also cover what each option can and cannot do, and the risks of each.
About the cause
- Is this line from movement, from lost volume, or both?
- Does it stay when my face is still?
- Is the skin itself part of the picture?
- Would treating one cause leave another untouched?
About the treatment
- What will this treatment not change?
- What are its main risks in this area?
- Which type of filler is planned, and can it be reversed?
- When is the review visit, and what happens there?
Bring a list of your medicines and any past treatments to the first visit. The doctor assesses the area and photographs it before filler. Before the toxin, you are asked to make expressions so the muscles' strength can be judged.
Some people should wait, and for some a treatment is ruled out. At Nexus, the toxin waits during pregnancy or breastfeeding, and it is not given to anyone with a condition of the nerves and muscles, such as myasthenia gravis or Lambert-Eaton syndrome. Filler waits during pregnancy or breastfeeding, and while there is active acne or a skin infection where it would go. It is not used in anyone allergic to hyaluronic acid or to another part of the filler.
Take these questions with you to a consultation. You can read more about each treatment on our anti-wrinkle injection and dermal fillers pages.
