📅 23 August 2026🏷 Botox Alternatives

Dysport Side Effects: What the Trials Actually Found

By Lucas, Founder & Lead Researcher

Reviewed for medical accuracy against our Medical Review Board · Last updated 23 August 2026

Dysport's glabellar trials put headache at 9% against 5% on placebo, eyelid drooping at 2% against under 1%, and any adverse reaction at all at 48% against 33%. Those placebo columns are the part nobody publishes, and they change how you read the numbers. Meanwhile the question people actually worry about, whether it stops working over time, has an answer in the label that is better than anything you will read elsewhere: across 1,554 patients treated for up to nine cycles, not one developed a neutralising antibody.

A gloved clinician placing an injection near the outer brow of a patient wearing a surgical cap, against a plain white background — The label is specific about this region: medial corrugator injections belong at least a centimetre above the bony brow ridge, and the eyelid muscle is to be avoided. Placement is what keeps the 2% at 2%.

Everything on this page is from the prescribing information, with the placebo comparison attached wherever the label provides one. There is also a boxed warning, and it is here in full, because a page that leaves one out to sound reassuring is not being kind to you.

1. The common side effects, with placebo rates

This table is from the glabellar lines trials: 398 patients on Dysport, 496 on placebo. The placebo column is the important one, and it is the column every other page drops.

Adverse reactions in the Dysport glabellar trials, against placebo
Reaction	Dysport (n=398)	Placebo (n=496)
Any adverse reaction	48%	33%
Nasopharyngitis (cold symptoms)	10%	4%
Headache	9%	5%
Injection site pain	3%	2%
Injection site reaction	3%	under 1%
Upper respiratory tract infection	3%	2%
Eyelid swelling	2%	0%
Eyelid drooping (ptosis)	2%	under 1%
Sinusitis	2%	1%
Nausea	2%	1%
Blood present in urine	2%	under 1%

Read down the two columns and the shape of it becomes clear. A third of people who were injected with nothing reported an adverse reaction. Ten percent of the Dysport group caught a cold, against 4% of the placebo group, and a wrinkle treatment does not cause colds; that is what happens when you ask several hundred people to write down every symptom for months. Nausea, sinusitis and injection site pain sit one point apart from placebo.

The reactions where Dysport clearly separates from placebo are the ones worth your attention: headache, eyelid swelling and eyelid drooping. Those three are the real list.

2. Headache, the most searched of all

More people search for whether Dysport causes headaches than for any other single side effect, and almost no page gives them a figure. Here it is: 9% of Dysport patients reported headache, against 5% of placebo patients.

So yes, it causes headaches, and the honest framing is that roughly one in twenty-five people gets a headache attributable to the treatment rather than to being a person who sometimes gets headaches. The label does not describe them as severe, and they are not listed among the serious reactions.

What the label does not tell you is why, and anyone who claims certainty there is guessing. The plausible explanations are the injections themselves, the muscles of the brow being newly unable to do what they were doing, and the tension of the appointment. Practically, they tend to arrive in the first few days and settle as the muscle relaxation completes.

Two things are worth knowing. A headache that starts within a week and eases is the pattern in the trials. A headache that is severe, keeps getting worse, or comes with vision changes, difficulty swallowing or muscle weakness is not that pattern, and belongs in section 12 below rather than in a list of expected effects. And if you are hoping the treatment will help your headaches, note that Botox rather than Dysport is the product approved for chronic migraine, on a specific protocol covered in our page on therapeutic uses.

3. Droopy eyelid and dry eye

Eyelid drooping ran at 2% against under 1% on placebo, and eyelid swelling at 2% against zero. These are the effects that genuinely bother people, so the label's detail is worth having.

Most cases were mild to moderate and resolved over several weeks. The rate did not increase across long-term studies with repeated treatments at intervals of three months or more, so it is not a risk that accumulates. And it is dose-dependent: the label states plainly that patients given higher doses had a higher incidence, which is worth remembering if you are tempted to ask for extra units to make a result last longer.

The label also gives two concrete technique points that reduce it, and they are fair to ask about: medial corrugator injections should be placed at least one centimetre above the bony ridge of the brow, and injection near the levator palpebrae superioris, the muscle that lifts the lid, should be avoided. Our page on a droopy eyelid after treatment covers what to do while you wait for it to pass, and the short version is that it passes.

Separately there is a dry eye warning specific to glabellar treatment, added to the label in September 2023, which instructs referral for anyone who develops persistent eye dryness or irritation. Dry eye also appears in the post-approval reports. It is not on most competing pages, and knowing it exists is the difference between mentioning it to someone and assuming it is unrelated.

4. The boxed warning, in full

Dysport carries a boxed warning, the FDA's most serious category. Every botulinum toxin product has the same one. It reads:

The effects of DYSPORT and all botulinum toxin products may spread from the area of injection to produce symptoms consistent with botulinum toxin effects. These symptoms have been reported hours to weeks after injection. Swallowing and breathing difficulties can be life-threatening and there have been reports of death. The risk of symptoms is probably greatest in children treated for spasticity but symptoms can occur in adults, particularly in those patients who have underlying conditions that would predispose them to these symptoms.

The context that makes this readable rather than terrifying: the warning applies across the whole product class, and the risk it describes is concentrated in therapeutic dosing. A child treated for spasticity may receive many hundreds of units into large limb muscles. A glabellar treatment is 50 units into two small muscles of the face. The warning is on the label of both because it is the same molecule, not because the two situations carry the same risk.

It is still the reason the symptoms in section 12 are worth memorising, and the reason "hours to weeks after injection" matters: a problem appearing two weeks later is not automatically unrelated. If you want the fuller version of how a purified therapeutic protein relates to the illness it comes from, our page on Botox against botulism covers it.

5. Who should not have Dysport at all

The contraindications are short and absolute. Dysport should not be given to anyone with:

Known hypersensitivity to any botulinum toxin product, to any component of the formulation, or to cow's milk protein.
Infection at the proposed injection site.

The cow's milk one surprises almost everybody, and it is the single most useful thing on this page for the people it applies to. Dysport contains lactose, and the label states the product may contain trace amounts of cow's milk protein. Botox has no equivalent contraindication. If you have a diagnosed cow's milk protein allergy, this is a hard reason to choose a different brand, and it will not come up unless you raise it, because nobody asks about dairy before a wrinkle treatment.

Note the distinction that matters here: this is about allergy to milk protein, not lactose intolerance, which is a different thing entirely and is not a contraindication.

Beyond the absolute contraindications, the label flags pre-existing neuromuscular disorders such as myasthenia gravis, ALS or Lambert-Eaton syndrome as conditions where patients may be at increased risk of serious effects, including swallowing and breathing difficulty. Anyone in that group needs a conversation with a neurologist rather than an aesthetics consultation.

6. Long-term effects, and whether it stops working

"Long-term side effects of Dysport" is a heavily searched phrase and the honest answer to it is undramatic. The label reports no distinct set of long-term harms, and it reports that in the clinical trials database, where some patients received up to twelve treatments, adverse reactions occurred in 57% of patients and were dominated by the same unremarkable list: headache, cold symptoms, injection site pain and bruising.

The real long-term worry people have is different from the one they type. It is whether the treatment stops working. Here the label is unusually specific and unusually reassuring:

Testing for antibodies to Dysport was performed for 1,554 subjects who had up to nine cycles of treatment. Two subjects tested positive for binding antibodies at baseline. Three additional subjects tested positive after receiving Dysport. None of the subjects tested positive for neutralising antibodies.

Neutralising antibodies are the ones that would actually stop it working. Across 1,554 people and up to nine rounds of treatment, nobody developed any. For comparison the label reports about 3% antibody formation in cervical dystonia patients, who receive vastly larger doses, which is the pattern you would expect: resistance is a dose problem, and cosmetic doses are small.

So if your Dysport seems to be working less well than it used to, immunity is the least likely explanation. Far more often it is the dose, the interval, a different injector's placement, or an accurate memory of the first result competing with an inaccurate memory of the second. Our page on how long Dysport lasts covers the wearing-off pattern, and the myths page covers where the immunity idea came from.

7. How long side effects last

The label gives one direct figure: most reports of eyelid drooping were mild to moderate and resolved over several weeks. For the rest, the underlying logic is what tells you the timeline, because the effect wears off on its own schedule and any side effect caused by muscle relaxation goes with it.

Needle effects, meaning injection site pain, redness, bruising and small bumps: hours to a few days.
Headache: typically the first few days, settling as the muscle relaxation completes.
Anything caused by the muscle relaxation itself, including a dropped brow, an uneven smile or a heavy lid: this is the one people find hard to hear. It lasts as long as the treatment does. The label says the clinical effect may last up to four months, so a placement problem follows that same curve. It cannot be reversed or dissolved, only waited out, which is precisely why who injects you matters more than what you pay.

8. Rare and post-approval reports

Beyond the trials, the label lists reactions identified after approval. These come from voluntary reporting, so no rate can be calculated and causation is not established, but they are on the label and you deserve to see them: vertigo, photophobia, influenza-like illness, muscle wasting, burning sensation, facial paresis, reduced sensation, redness, dry eye, and excessive granulation tissue. Hypersensitivity reactions including anaphylaxis have been reported.

Facial paresis, meaning weakness of facial muscles beyond the intended target, is the one on that list that connects back to the boxed warning. It is rare enough to have no measured frequency, and it is a reason to take unexpected weakness seriously rather than waiting to see.

9. Medicines that interact with it

Four categories, from the label:

Aminoglycoside antibiotics and other agents that interfere with neuromuscular transmission: the effect of the toxin may be potentiated.
Anticholinergic drugs: taken after Dysport, these may potentiate systemic anticholinergic effects such as blurred vision.
Other botulinum toxin products: the effects of overlapping treatments may be additive, which is the reason for the three month minimum interval and a reason to tell a new injector what you have had recently, and when.
Muscle relaxants: also a potential additive effect.

None of these is a reason to avoid treatment. All of them are reasons the medication question on the consultation form is not a formality.

10. What "Dysport gone wrong" usually means

"Dysport gone wrong" and "bad Dysport results" are searched a few hundred times a month between them, and almost none of it is a safety event. Sorted by how often it actually happens:

Too much, in the wrong place. A dropped brow, a frozen forehead, an eyebrow that sits higher than the other. Placement, not the product, and it wears off.
Too little, or too far apart. A result that barely showed or faded in six weeks. Underdosing is far commoner than overdosing, and it is worth knowing that the labelled glabellar dose is 50 units before you accept a quote well below it.
The wrong expectation. Lines visible when the face is completely still are creases in the skin, and no toxin at any dose removes them. The label's own screening test is to spread the skin apart with your fingers: if the line stays, a toxin is not the treatment for it.
A unit count that looked alarming. Fifty units sounds like a lot next to twenty of Botox and is the same treatment. This one is arithmetic rather than a bad outcome, and the units comparison covers it.

Three of those four are avoided at the consultation rather than fixed afterwards.

11. Is Dysport safer than Botox?

No, and neither is safer than the other. They carry the same boxed warning, the same class of effects, and comparable rates in their own trials. Two real differences exist and neither makes one product safer overall:

Dysport is contraindicated in cow's milk protein allergy. Botox is not. For that group, Botox is the safer choice, unambiguously.
Dysport is generally understood to spread a little further from each injection point. That is a placement consideration rather than a safety ranking: helpful on a broad forehead, less so around the mouth or near the eyelid, as our page on Dysport treatment areas sets out.

Comparing the trial percentages between the two labels directly is not a sound method, because the trials had different sizes, endpoints and reporting periods. The full head-to-head is in our Dysport against Botox comparison.

12. When to call someone

Most of this page describes minor and self-limiting effects. This section does not. The label's guidance is to seek immediate medical attention for symptoms of distant spread, which can appear hours to weeks after injection:

Difficulty swallowing, or the feeling that food is sticking
Difficulty breathing or shortness of breath
Difficulty speaking, or a change in the sound of your voice
Muscle weakness away from the injection site, or general loss of strength
Double vision, blurred vision, or new drooping of the eyelids
Loss of bladder control

Also worth a same-day call: signs of an allergic reaction, meaning swelling of the face, lips, tongue or throat, hives, wheezing, or feeling faint. Anaphylaxis has been reported.

Everything else, including a headache in the first few days, a bruise, or an eyelid that looks a little heavy, is a message to your injector rather than an emergency. Tell them anyway. A good one wants to know, and a record of what happened at what dose is what makes your next treatment better.

Frequently asked questions

What are the most common side effects of Dysport?

In the glabellar trials the reactions that clearly exceeded placebo were headache (9% against 5%), eyelid swelling (2% against 0%) and eyelid drooping (2% against under 1%). Injection site pain, bruising and redness are common but sat within a point or two of placebo. Worth knowing that 33% of people who received a placebo injection also reported some adverse reaction, which is the context that makes the Dysport numbers readable.

Does Dysport cause headaches?

Yes, in about 9% of patients against 5% on placebo, so roughly one in twenty-five people gets a headache attributable to the treatment itself. They typically arrive in the first few days and settle as the muscle relaxation completes, and the label does not characterise them as severe. A headache that is severe, worsening, or accompanied by vision changes, difficulty swallowing or muscle weakness is a different matter and needs prompt medical attention.

How long do Dysport side effects last?

Needle-related effects such as pain, redness and bruising last hours to a few days. Headaches usually settle within the first week. Eyelid drooping was mostly mild to moderate and resolved over several weeks in the trials. The important exception is anything caused by the muscle relaxation itself, such as a dropped brow or an uneven smile: that lasts as long as the treatment does, up to about four months by the label, and cannot be reversed or dissolved.

Can Dysport cause a droopy eyelid?

It can, at 2% against under 1% on placebo in the glabellar trials. Most cases were mild to moderate and resolved over several weeks, and the rate did not increase with repeated treatments spaced three months or more apart. The label notes it is dose-dependent, and gives two specific technique points that reduce it: medial corrugator injections placed at least one centimetre above the bony brow ridge, and avoiding injection near the levator palpebrae superioris.

Does Dysport have a boxed warning?

Yes, and so does every botulinum toxin product. It warns that effects may spread from the injection site to cause botulinum toxin symptoms, reported hours to weeks afterwards, and that swallowing and breathing difficulties can be life-threatening, with reports of death. The label states the risk is probably greatest in children treated for spasticity, who receive many hundreds of units into large limb muscles. A cosmetic glabellar treatment is 50 units into two small facial muscles. Same warning, very different exposure.

Who should not get Dysport?

Anyone with known hypersensitivity to a botulinum toxin product, to any component of the formulation, or to cow's milk protein, and anyone with an infection at the injection site. The cow's milk contraindication is specific to Dysport, which contains lactose and may contain trace milk protein; Botox has no equivalent. The label also flags pre-existing neuromuscular disorders such as myasthenia gravis, ALS or Lambert-Eaton syndrome as carrying increased risk of serious effects.

Can you be allergic to Dysport?

Yes. Known hypersensitivity to any botulinum toxin product or to any formulation component is an absolute contraindication, and hypersensitivity reactions including anaphylaxis have been reported after approval. Signs needing immediate attention are swelling of the face, lips, tongue or throat, hives, wheezing, difficulty breathing or feeling faint. Because Dysport may contain trace cow's milk protein, a diagnosed milk protein allergy is a reason to choose a different brand. Lactose intolerance is a different condition and is not a contraindication.

What are the long-term side effects of Dysport?

The label reports no distinct set of long-term harms. In the clinical trials database, where some patients had up to twelve treatments, 57% reported some adverse reaction and the list was dominated by headache, cold symptoms, injection site pain and bruising. The rate of eyelid drooping did not increase with repeated treatment at intervals of three months or more.

Can your body become immune to Dysport?

The label's data on this is stronger than most people expect. Antibody testing was done on 1,554 patients treated for glabellar lines across up to nine cycles. Three developed binding antibodies after treatment, and none developed neutralising antibodies, which are the ones that would actually stop it working. By contrast about 3% of cervical dystonia patients, who receive far larger doses, developed antibodies. If your results seem weaker over time, dose, interval or injector technique are far likelier explanations than immunity.

Is Dysport safer than Botox?

Neither is safer than the other. They share the same boxed warning, the same class of side effects, and comparable rates in their own trials, and comparing percentages across two labels is not sound because the trials differed in size, endpoints and reporting. There is one clear exception: Dysport is contraindicated in cow's milk protein allergy and Botox is not, so for that group Botox is unambiguously the safer choice.

What does it mean when people say Dysport went wrong?

Almost always placement rather than a safety event. The usual four are too much product in the wrong spot, giving a dropped brow or a frozen forehead; too little product or too long an interval, giving a result that barely showed; an expectation a toxin cannot meet, because lines visible at complete rest are creases in the skin rather than muscle activity; and alarm at a unit count that is simply measured on a different scale. Three of the four are settled at the consultation, not afterwards.

Can Dysport be reversed if I do not like the result?

No. There is no reversal agent for any botulinum toxin, unlike hyaluronic acid fillers which can be dissolved. If the placement is wrong you wait it out, and the label says the clinical effect may last up to four months. In some cases a skilled injector can partially rebalance the appearance by treating an opposing muscle, but that adds product rather than removing it. This is the strongest practical argument for choosing your injector on experience rather than on price per unit.

Does Dysport interact with any medications?

Four categories are on the label. Aminoglycoside antibiotics and other agents interfering with neuromuscular transmission may potentiate the toxin's effect. Anticholinergic drugs taken afterwards may potentiate systemic effects such as blurred vision. Other botulinum toxin products may be additive, which is part of why the minimum interval is three months. Muscle relaxants may also be additive. None of these rules out treatment, but all of them are reasons to complete the medication question honestly.

Written by

Lucas Pradella

Founder & Lead Researcher, BestBotoxClinics.com

Lucas founded BestBotoxClinics.com to bring clarity to the aesthetics industry, bringing 13+ years of experience in digital research and analysing online data for signals of quality and trust. He is not a physician, his work is research, data analysis and verifying provider credentials.

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Medical accuracy: BestBotoxClinics.com maintains a Medical Review Board of licensed clinicians. This article is educational and is not medical advice.