Botulinum toxin is one of the most widely used non-surgical treatments in aesthetic medicine. Its popularity can make it feel routine, but the pharmacology is not trivial: the treatment changes neuromuscular signaling. The same mechanism that softens dynamic lines can also produce unwanted weakness if the effect extends beyond the intended muscle, or if the dose, depth, distribution, or patient anatomy are not appropriately matched.
This guide explains Botox side effects and safety for patients in Abu Dhabi, based on a pharmacovigilance study of adverse events reported to the US Food and Drug Administration Adverse Event Reporting System (FAERS) for Botox/Botox Cosmetic, Dysport, and Xeomin.
Why a Detailed Botox Safety Guide Matters
The investigators did not set out to calculate the true incidence of side effects. Instead, they looked for patterns in spontaneous reports and used disproportionality statistics to determine whether selected adverse events appeared more often than expected in the reporting database.
This distinction is essential for patient education. A database signal can help identify an adverse event that deserves attention, but it does not tell an individual patient how likely that event is, and it cannot by itself prove causation.
How Botulinum Toxin Works—and Why Side Effects Are Biologically Plausible
Botulinum toxin inhibits acetylcholine release at the neuromuscular junction of striated muscle. This produces chemical denervation and a temporary reduction in muscle contraction. When carefully titrated, the same mechanism is useful for both cosmetic and therapeutic indications.
Because the effect is neuromuscular, adverse events involving weakness are not mysterious. If the intended target is the glabellar complex but nearby functional muscle is affected, eyelid or brow position can change. If treatment in another region spreads or influences adjacent structures, the patient may experience facial asymmetry, weakness, swallowing difficulty, or other functional symptoms.
Botulinum toxin is also used for therapeutic conditions including blepharospasm, cervical dystonia, spasticity, facial palsy, altered exocrine gland function, voice disorders, and other neuromuscular conditions. This matters because FAERS combines reports from patients treated for very different indications and at very different dose ranges.
What the FAERS Study Actually Analyzed
The investigators queried FAERS through an openFDA-based tool. Botox and Botox Cosmetic were analyzed together under onabotulinumtoxinA, Dysport as abobotulinumtoxinA, and Xeomin as incobotulinumtoxinA. The authors first identified frequent adverse events and then focused on events of clinical significance: eyelid or eyebrow ptosis, asthenia, muscular weakness, facial paresis, dysphagia, botulism, and death.
Healthcare professionals, consumers, and manufacturers can submit adverse-event reports. Manufacturers have mandatory reporting obligations for certain events, while clinicians and patients may report voluntarily. All reports are coded using standardized adverse-event terminology.
Understanding PRR and ROR in Plain Language
The study used two disproportionality measures: proportional reporting ratio (PRR) and reporting odds ratio (ROR). These statistics ask whether a particular adverse event is reported disproportionately often with a specific product compared with its background reporting frequency in the wider database.
A high PRR or ROR can generate a safety signal. A signal means the pattern deserves attention; it does not mean that the event was definitely caused by the product. The authors used conventional statistical thresholds, including whether the lower limit of the 95% confidence interval for the ROR was greater than 1.
How Many Adverse-Event Reports Were in the Database?
Botox/Botox Cosmetic had 38,367 adverse-event reports in the dataset used by the investigators, Dysport had 3,582, and Xeomin had 1,405. These raw totals should not be used to rank the products by safety, because the formulations differ in market history, utilization, indications, dosing, and exposure.
| Product group | Total FAERS adverse-event reports |
|---|---|
| Botox + Botox Cosmetic (onabotulinumtoxinA) | 38,367 |
| Dysport (abobotulinumtoxinA) | 3,582 |
| Xeomin (incobotulinumtoxinA) | 1,405 |
The Most Frequently Reported Events for Each Product
The study listed the top ten reported adverse events for each product category. The percentages below represent the proportion each event made up of all adverse-event reports for that specific product in the database; they are not the percentage of all treated patients who experienced the event.
| Rank | Botox / Botox Cosmetic | Dysport | Xeomin |
|---|---|---|---|
| 1 | Drug ineffective — 2.66% | Dysphagia — 2.60% | Drug ineffective — 1.64% |
| 2 | Headache — 1.51% | Muscular weakness — 2.21% | Headache — 0.71% |
| 3 | Nausea — 1.00% | Drug ineffective — 2.04% | Injection-site pain — 0.71% |
| 4 | Muscular weakness — 0.99% | Fatigue — 1.84% | Therapeutic response decreased — 0.71% |
| 5 | Fatigue — 0.96% | Dyspnea — 1.79% | Dysphagia — 0.64% |
| 6 | Pain — 0.93% | Headache — 1.70% | Eyelid ptosis — 0.57% |
| 7 | Dysphagia — 0.90% | Overdose — 1.65% | Influenza-like illness — 0.57% |
| 8 | Migraine — 0.86% | Eyelid ptosis — 1.59% | Periorbital edema — 0.50% |
| 9 | Dyspnea — 0.82% | Asthenia — 1.45% | Dry eye — 0.43% |
| 10 | Asthenia — 0.81% | Product-preparation error — 1.09% | Dyspnea — 0.43% |
These lists show what was reported frequently in FAERS, but they cannot be read as a head-to-head clinical trial. The database contains different indications, doses, patient populations, and exposure levels across the products.
Expected Injection Reactions vs. Unwanted Pharmacologic Effects
The study separates adverse effects into two broad groups:
- Injection reactions: mild erythema (redness), bruising, edema (swelling), and tenderness at the injection site. These are expected and usually short-lived. Headache can also occur after facial injections and is generally mild, resolving within a few days.
- Undesired pharmacologic effects: these occur less frequently and are primarily related to temporary denervation of adjacent muscles outside the intended treatment area.
This distinction is clinically useful because a small bruise and eyelid ptosis arise from different mechanisms and require different counseling.
Eyelid Ptosis After Botox: One of the Clearest Safety Signals
Eyelid ptosis was one of the strongest and most consistent findings. Across the products with reported cases, PRR values ranged from 9.49 to 26.10, and the corresponding ROR confidence intervals met the authors’ signal criteria.
| Product | Cases | PRR | ROR | Interpretation in study |
|---|---|---|---|---|
| Botox / Botox Cosmetic | 261 | 12.13 | 12.20 | Signal |
| Dysport | 52 | 26.10 | 26.47 | Signal |
| Xeomin | 7 | 9.49 | 9.53 | Signal |
The authors describe eyelid ptosis as a known and well-established adverse effect of botulinum toxin. They also note a therapeutic parallel: botulinum toxin has intentionally been used to produce temporary ptosis for corneal protection in selected ophthalmologic conditions, which reinforces how directly ptosis relates to the toxin’s neuromuscular action.
Eyebrow Ptosis
Eyebrow ptosis also generated elevated disproportionality values. Botox/Botox Cosmetic had 21 reported cases with a PRR of 17.60 and ROR of 17.61. Dysport had 2 reported cases with similarly elevated ratios. Xeomin was not listed among the top 300 adverse events ranked by PRR for this event.
For aesthetic patients, the practical distinction between brow heaviness and true eyelid ptosis should be explained during consultation. Both can be experienced as “drooping,” but they reflect different anatomic effects.
Asthenia, Muscular Weakness, and Facial Paresis
Asthenia was reported in the database, but the study did not identify significant PRR/ROR signals for asthenia across the analyzed formulations. Muscular weakness showed a more mixed picture: Dysport reached the signal criteria, while for Botox/Botox Cosmetic the ROR confidence interval exceeded 1 but the PRR did not meet the same threshold. Xeomin did not show a significant signal.
Facial paresis produced a clearer pattern for Botox/Botox Cosmetic and Dysport, with PRRs of 10.91 and 12.65 and RORs of 10.94 and 12.68, respectively.
| Event | Botox / Botox Cosmetic | Dysport | Xeomin |
|---|---|---|---|
| Asthenia | PRR 0.39 / ROR 0.38 | PRR 0.74 / ROR 0.73 | PRR 0.15 / ROR 0.15 |
| Muscular weakness | PRR 1.43 / ROR 1.44 | PRR 3.35 / ROR 3.41 | PRR 0.37 / ROR 0.34 |
| Facial paresis | PRR 10.91 / ROR 10.94 | PRR 12.65 / ROR 12.68 | Not listed |
Why Facial Paresis Is Difficult to Interpret From FAERS Alone
Botulinum toxin is itself used to treat facial paralysis-related asymmetry, hyperkinesis, and synkinesis. Some FAERS entries coded as facial paresis may therefore reflect the underlying condition being treated rather than a new adverse event caused by the injection.
At the same time, the authors acknowledge that overtreatment of a target muscle can produce weakness or paresis. It is a good example of why spontaneous-report databases can raise a signal without resolving causality.
Dysphagia: A Spread-Related Symptom Worth Understanding
Dysphagia (swallowing difficulty) can occur when toxin effects extend beyond the intended target. In the study, Dysport met both PRR and ROR signal criteria (PRR 5.06, ROR 5.17). Botox/Botox Cosmetic had a PRR of 1.70 and ROR of 1.70, with the ROR confidence interval meeting the signal criterion while the PRR did not. Xeomin did not meet the reported thresholds.
The literature is nuanced. Botulinum toxin can cause dysphagia in some treatment contexts, but it is also injected therapeutically into selected swallowing-related structures to treat certain forms of dysphagia. The same symptom can therefore appear in the database as an adverse event or as the underlying indication.
Botulism-Like Effects and Systemic Spread
Botulism generated very high disproportionality values for Botox/Botox Cosmetic and Dysport.
| Product | Reported cases | PRR | ROR |
|---|---|---|---|
| Botox / Botox Cosmetic | 33 | 40.74 | 40.77 |
| Dysport | 13 | 174.93 | 175.57 |
| Xeomin | Not listed in the table for this event | ||
These large ratios should not be interpreted as large absolute risks. Botulism reports were uncommon in absolute count relative to total adverse-event reports. A disproportionality statistic becomes large when an event is far more concentrated among reports for a drug than in the background database.
The article describes dysphagia, breathing difficulty, generalized weakness, paralysis, and botulism-like symptoms as potentially serious manifestations of spread. It also notes that botulism-like symptoms in therapeutic use have sometimes occurred in the context of underlying, previously undiagnosed neuromuscular disease such as myasthenia gravis.
What Did the Study Find About Death Reports?
The database contained 79 death reports for Botox/Botox Cosmetic, 5 for Dysport, and 1 for Xeomin. However, the PRR and ROR values for death were all below 0.05 and did not meet the study’s disproportionality signal criteria.
The authors also state that death had not been documented after properly administered, standard approved formulations for cosmetic indications in the literature they reviewed. Some cases in which Botox was assumed to be involved were attributed to mechanisms such as anaphylaxis, allergy, or hypersensitivity rather than the expected neuromuscular mechanism.
Why Injection Technique Matters
Many unwanted effects are technique-dependent. Precise area and depth are important because the goal is to affect a target muscle while avoiding unnecessary spread to adjacent functional structures. The authors state that complication incidence decreases as injector skill improves.
The paper also discusses injection volume and concentration. Botulinum toxin is reconstituted before use, and different dilutions alter the concentration delivered in a given volume. The authors argue that consistent technique and careful attention to injection volume can reduce unwanted asymmetry and adverse effects.
For less experienced injectors, the source cites recommendations favoring conservative dosing and reassessment rather than aggressive initial treatment. The broader principle is simple: treatment should be individualized rather than based on a fixed dose copied from a standard template.
Dose Matters—but It Is Not the Only Variable
Adverse effects can be dose-related. Muscle mass, habitual facial expression, skeletal frame size, and facial morphotype can also affect dosing requirements. The paper cites evidence that men may require higher doses than women for the same aesthetic effect because of differences in muscle mass, and cites consensus work showing that facial morphotypes vary across populations.
This does not mean demographic category alone should determine dose. It supports an anatomy- and function-based approach: observe the patient’s muscle strength, movement pattern, facial proportions, and treatment objective before deciding how much product to use.
Botox vs. Dysport vs. Xeomin: Why Raw Report Counts Can Mislead
Botox/Botox Cosmetic had far more adverse-event reports than Dysport or Xeomin, but this may reflect exposure rather than greater risk. Botox had earlier FDA approval and was more widely used. The products also differ in potency characteristics and approved therapeutic recommendations.
Neurology guidelines distinguish between formulations for therapeutic indications, reinforcing an important clinical principle: units are product-specific and should not be treated as directly interchangeable without formulation-specific knowledge.
The authors observed that Dysport had higher PRR/ROR values across several studied adverse events and discuss preclinical safety-margin research and therapeutic crossover studies. However, FAERS cannot provide a definitive head-to-head safety ranking, because exposure, indication, dose, reporting behavior, and market history are different.
Cosmetic vs. Therapeutic Use: Do Not Mix Them Up
Therapeutic treatment may involve different muscles, higher total doses, different injection patterns, and patients with underlying neurologic disease. Earlier FDA adverse-event reviews cited by the paper found that serious adverse events were more likely in therapeutic indications than in cosmetic ones.
For a cosmetic patient, this means the most frightening events in a pharmacovigilance database may not reflect the risk profile of a standard aesthetic treatment in a healthy patient. At the same time, those reports support careful screening, dosing, technique, and informed consent.
Which Symptoms Are Expected, and Which Are Not Routine?
| Category | Examples | What it generally means |
|---|---|---|
| Expected short-term effects | Mild redness, bruising, tenderness, swelling, short-lived headache | Common injection-related effects, usually short-lived |
| Symptoms that deserve medical assessment | Progressive weakness, swallowing difficulty, shortness of breath, marked facial dysfunction, symptoms extending well beyond the treatment area | Not routine aftercare; contact your clinic or seek urgent medical review |
Patients should be given a clear post-treatment contact pathway. The article does not provide a patient emergency algorithm, but its discussion of dysphagia, breathing difficulty, systemic spread, weakness, and botulism-like effects supports treating such symptoms as clinically important rather than routine.
Patient Selection and Informed Consent
The authors recommend that providers remain aware of eyelid or brow ptosis, facial paresis, botulism-like effects, and other relevant adverse events, and include clinically important possibilities in informed consent.
A high-quality consultation should not simply list complications. It should explain which effects are expected, which are uncommon, what factors may change risk, what recovery looks like, and what symptoms require review. It should also clarify that individual risk depends on treatment area, indication, dose, product, anatomy, previous response, and medical history.
What the FAERS Database Cannot Tell Us
- FAERS includes consumer reports, and the investigators could not verify the accuracy of every submission.
- The database did not identify what proportion of reports came from physicians, patients, or manufacturers, so reporter bias is possible.
- Duplicate reporting is possible: the same event may be submitted separately by the patient, clinician, and manufacturer, inflating counts.
- FAERS cannot establish causality. An event reported after a drug was used does not prove the drug caused it.
The authors explicitly state that the findings are not intended to change practice guidelines. Their purpose is to highlight potential complications that may or may not result from botulinum toxin injection.
What This Study Supports—and What It Does Not
| Supported by the study | Not supported by the study |
|---|---|
| Eyelid and brow ptosis are well-established adverse effects and generated strong reporting signals. | Using FAERS report counts to calculate the true complication rate in cosmetic patients. |
| Facial paresis and botulism generated significant disproportionality signals for some formulations. | Concluding that one product is definitively safer or more dangerous from raw FAERS counts. |
| Dysphagia and generalized weakness are clinically important because they may relate to spread beyond the intended target. | Assuming every event reported after injection was caused by the toxin. |
| Technique, dose, injection volume, and individualized anatomy can influence unwanted effects. | Applying therapeutic-dose adverse-event patterns directly to a standard cosmetic patient without context. |
A Practical Patient Checklist Before Botox Treatment
- Confirm that a qualified clinician has assessed the treatment area rather than relying only on a standard injection map.
- Tell the clinician about previous botulinum toxin treatments, previous adverse effects, neurologic or neuromuscular disease, and relevant medications.
- Ask what degree of movement the clinician intends to preserve and what functional trade-offs are possible in the chosen treatment area.
- Ask which post-treatment effects are expected and which symptoms should prompt a call or urgent review.
- Make sure the product and dose are documented and that the clinic has a follow-up pathway if asymmetry or functional symptoms occur.
- Understand that more units do not automatically mean a better or longer-lasting cosmetic result.
Key Findings From the Study
- 38,367 adverse-event reports were identified for Botox/Botox Cosmetic, 3,582 for Dysport, and 1,405 for Xeomin.
- Eyelid ptosis generated significant PRR and ROR signals for all products with reported cases.
- Eyebrow ptosis produced significant signals for Botox/Botox Cosmetic and Dysport.
- Facial paresis produced significant reporting signals for Botox/Botox Cosmetic and Dysport.
- Dysport met the authors’ signal criteria for muscular weakness and dysphagia.
- Botulism produced very high disproportionality ratios for Botox/Botox Cosmetic and Dysport, but the absolute number of reports was small relative to total reports.
- Death reports were present, but PRR and ROR values for death were not significant.
- FAERS cannot establish causality and may contain unverified or duplicate reports.
Frequently Asked Questions About Botox Safety
Is Botox generally considered safe?
The source states that botulinum toxin is generally considered safe and tolerable across a wide range of aesthetic and therapeutic applications. Adverse events still occur, so safe use depends on indication, patient selection, formulation, dose, technique, and follow-up.
What are the most common short-term Botox side effects?
Mild erythema, bruising, edema, tenderness, and short-lived headache are the expected injection-related effects.
Is eyelid ptosis a real Botox complication?
Yes. Eyelid ptosis is a known and well-established adverse effect and generated strong disproportionality signals in the FAERS analysis.
Does a high PRR mean the complication is common?
No. PRR measures disproportionate reporting, not absolute incidence. A high PRR can occur for a rare event if that event is unusually concentrated among reports for a drug.
Does FAERS prove Botox caused an adverse event?
No. The authors explicitly state that causality cannot be established from the database.
Can Botox cause facial weakness?
Temporary unwanted weakness can occur if adjacent muscles are affected or if treatment is excessive for the target. Facial paresis also generated reporting signals, although some reports may reflect pre-existing facial paralysis being treated with Botox.
Can Botox cause swallowing difficulty?
Dysphagia is a recognized adverse event in some treatment contexts and can be associated with spread beyond the intended target. Botulinum toxin is also used therapeutically to treat selected forms of dysphagia, which complicates interpretation of spontaneous reports.
What is botulism-like spread?
The term describes serious systemic toxin effects that may include swallowing difficulty, breathing symptoms, generalized weakness, or paralysis. Such events are clinically important but should not be read from FAERS ratios as a common cosmetic complication.
Did the study show Botox causes death?
No. Death reports existed in the database, but death did not generate a significant PRR/ROR signal, and FAERS cannot establish causation.
Is Dysport more dangerous than Botox because some PRRs were higher?
The study does not establish that. The products differ in potency, units, exposure, indications, market history, and reporting patterns. FAERS is not a randomized head-to-head safety trial.
Are Botox, Dysport, and Xeomin units interchangeable?
No. The source discusses meaningful formulation and potency differences and does not support simple unit-for-unit interchangeability.
What should I tell my doctor before treatment?
Share previous toxin response, medical and neuromuscular history, medications, treatment goals, and any prior adverse effects.
