What 40,000+ Safety Reports Tell Us About Cosmetic Neuromodulator

A 2026 analysis pooled 43,809 adverse event reports about cosmetic botulinum toxin type A from safety databases in the United States, Europe, Canada and Australia. The headline finding is reassuring for patients: most reports described the treatment not working as hoped or temporary local effects, while serious whole-body reactions were rare.

Why this was studied

Cosmetic neuromodulator injections are among the most common aesthetic treatments in the world. Clinical trials tell us a great deal about safety, but they involve a limited number of carefully chosen people. Once a medication is in wide use, regulators rely on "pharmacovigilance": systems where doctors, patients and manufacturers voluntarily report problems they believe may be linked to a drug.

Health Canada runs one of these systems, as do agencies in the United States, Europe and Australia. A team of UK researchers wanted to see what these databases, taken together, say about cosmetic use specifically.

What the researchers did

The team searched four national and regional databases covering roughly two decades of reports. They filtered for cosmetic uses, such as frown lines, forehead lines and crow's feet, and removed medical uses like migraine, excessive sweating and muscle spasm. They then grouped the reported problems into categories and counted them. This was a descriptive count; it did not test whether any effect happened more often than expected.

What they found

About 57% of reports involved the treatment seeming not to work, or working less well than before. Around 20% described injection-site effects such as pain, redness, swelling or bruising. About 10% mentioned drooping, weakness or unevenness of facial muscles, including eyelid or brow droop. Headache and skin reactions away from the injection site each appeared in about 6% of reports, and eye or vision complaints, such as double vision or dry eye, in about 5%. One report can list several problems, so the categories overlap.

Heart, breathing and allergic reactions together made up less than 1% of reports. Nearly nine in ten reports came from the United States database, with far fewer from Canada, Europe and Australia, which the authors interpret as a sign of under-reporting in other regions.

The authors also noticed that reports of the treatment not working often appeared alongside reports of off-label use, and that eyelid droop was often reported together with double vision or dry eye.

How strong is this evidence? How to read reporting data

Safety databases are valuable for spotting patterns, but they are easy to misread. Three points help.

• They cannot give a rate. No one knows how many treatments were performed in total, so 43,809 reports cannot be turned into "how likely is this to happen to me."
• They do not prove cause. A report means someone suspected a link, not that the injection caused the problem.
• Reporting is uneven. Most side effects are never reported, and some types, like disappointment with results, may be reported more often than others.

The paper also has some internal inconsistencies in date ranges and figures, which the authors acknowledge. Overall, this is a large but low-certainty source that complements, rather than replaces, clinical trials.

What it means for you

The pattern in these reports matches what clinicians see day to day. The most common concerns are temporary: a small bruise, a tender spot, a headache, or a result that is weaker or shorter-lived than hoped. Temporary drooping of an eyelid or brow is uncommon but well known, and it usually fades as the treatment wears off over weeks. Our article on neuromodulator side effects explains these in more detail.

A result that seems weak has many possible explanations, including dose, placement, how the product was prepared and stored, individual metabolism and, rarely, the body forming antibodies. If you feel your treatment has stopped working, our article on why a neuromodulator may seem to stop working covers the options.

Neuromodulator treatment is not suitable for everyone. People who are pregnant or breastfeeding, have certain nerve or muscle conditions, have an infection at the injection site, or take some specific medications are usually advised to avoid or delay it. Let your clinician know your full medical history and medication list.

If you develop difficulty swallowing, speaking or breathing after any injection, seek emergency care right away. These are very rare after cosmetic doses, but they are important to act on quickly.

You can also report a suspected side effect yourself to Health Canada through its online reporting system. Reports from patients help improve the picture for everyone.

Why safety reporting still matters

Even with its limits, voluntary reporting is how regulators spot unexpected problems once a medication is widely used. A cluster of similar reports can prompt a closer look, a label change or new guidance for clinicians. The authors argue that systems designed specifically for cosmetic treatments, and better sharing of data between countries, would make these signals clearer.

For patients, the practical point is simple. If something unexpected happens after treatment, tell the clinic that treated you so it can be assessed and documented. Clear records help your clinician plan future treatment safely, and they add to the wider safety picture.

Frequently asked questions

Do 43,809 reports mean the treatment is risky?

Not on its own. The number reflects many years of very widespread use across several countries, and most reports describe minor or temporary concerns. Without knowing how many treatments were given, it is impossible to calculate a rate.

Why are there so few Canadian reports?

The authors believe under-reporting is likely, both in Canada and elsewhere outside the United States. Fewer reports do not necessarily mean fewer problems.

Should I worry about eyelid droop?

It is uncommon and temporary. Careful dosing and placement lower the risk, and a clinician can discuss options if it happens.

If you have questions about neuromodulator safety, a consultation is a good place to talk through your history, expectations and any previous experiences with treatment.

Source

Zargaran A, Zargaran D, Pirayesh A, Woollard A, Mosahebi A. Global pharmacovigilance of aesthetic botulinum toxin type A: analysis of adverse event reports from the USA, Europe, Canada, and Australia. Journal of Cosmetic Dermatology, 2026. Read the study