Letybo vs. Botox Side Effects: Safety, Risks, and What Patients Should Know

Letybo vs. Botox Side Effects: What Is the Difference?

Letybo and Botox are both botulinum toxin type A products and share many potential adverse effects, including headache, injection-site reactions, bruising, and temporary eyelid or eyebrow drooping. The FDA-approved labeling for both products also contains a boxed warning about the possibility of distant spread of toxin effect, although serious systemic complications are uncommon with appropriately administered cosmetic treatment. Current evidence does not establish that either Letybo or Botox is universally safer than the other. The most important safety factors include the patient’s medical history, the treatment area, product-specific dosing, injection technique, and the experience of the injector.

If you’re trying to understand the broader differences between these two wrinkle relaxers; including their approved uses, treatment areas, duration, and clinical considerations- our Botox vs. Letybo: Complete Comparison provides a side-by-side overview.

At a Glance: Letybo vs. Botox Safety

The FDA labeling for both products emphasizes that botulinum toxin effects can extend beyond the intended injection site and that product-specific precautions must be followed.

What Are the Most Common Side Effects of Letybo?

According to the FDA prescribing information, headache was the most common adverse reaction reported with Letybo, occurring in 2% of treated patients in the clinical development program.

Other effects can occur after facial botulinum toxin injections, including:

• Injection-site pain or tenderness
• Redness
• Swelling
• Bruising
• Headache
• Temporary weakness of nearby muscles
• Eyelid drooping
• Eyebrow drooping
• Facial asymmetry

Not every event that occurs after an injection is necessarily caused by the medication. Clinical trials distinguish adverse events from events considered related to treatment, and spontaneous postmarketing reports cannot establish causation in every individual case.

In the Phase III Letybo trial involving 355 participants, letibotulinumtoxinA was described as well tolerated, with adverse events monitored during the study and repeat-treatment period.

What Are the Most Common Side Effects of Botox?

Botox Cosmetic can also cause temporary local and systemic adverse effects.

Depending on the treatment area, reported effects can include:

• Headache
• Injection-site pain
• Bruising
• Swelling
• Eyelid ptosis
• Brow ptosis
• Eyelid edema
• Facial weakness or asymmetry
• Dry eye or other ocular symptoms with periocular treatment

The precise adverse-effect profile depends partly on where Botox is injected.

For example, injections around the eyes have different potential complications from injections into the glabella or forehead.

The FDA labeling for Botox Cosmetic specifically describes ptosis, diplopia, dysphagia and generalized weakness among possible manifestations of spread of toxin effect.

Is Letybo Safer Than Botox?

There is currently no good basis for making that blanket claim.

This is an important distinction.

A clinical trial can demonstrate that a product was well tolerated under the conditions studied.

It does not establish that the product is universally safer than every competing botulinum toxin.

The direct Phase III comparison of Letybo with onabotulinumtoxinA was designed primarily to evaluate efficacy and noninferiority for glabellar lines; it does not establish a universal safety superiority of Letybo.

Similarly, the existence of a longer clinical history for Botox does not prove that Botox is inherently safer for every patient.

The evidence-supported conclusion is:

Both products have established safety profiles, but neither has been shown to be universally safer than the other for all cosmetic patients and treatment situations.

Safety is only one part of the decision, and questions about whether one product is preferable overall can involve factors beyond adverse effects. For a broader discussion, read Is Letybo better than Botox?

Why Can the Same Product Cause Different Side Effects in Different People?

Botulinum toxin is intended to temporarily reduce activity in selected muscles. The final result therefore depends on more than the drug itself.

Important variables include:

• Facial anatomy
• Muscle size
• Muscle strength
• Injection location
• Injection depth
• Dose
• Number of injection points
• Distance from neighboring muscles
• Existing asymmetry
• Previous treatment
• Individual susceptibility

This is particularly important around the eyes and eyebrows, where small changes in muscle activity can alter brow or eyelid position.

What Is Eyelid Ptosis?

Eyelid ptosis means drooping of the upper eyelid.

It is different from:

Brow ptosis

Drooping of the eyebrow.

Dermatochalasis

Excess or lax upper-eyelid skin.

These conditions can look similar to a patient but have different anatomical causes.

Botulinum toxin can occasionally cause eyelid or eyebrow drooping when the effect influences muscles that were not intended to be weakened. A systematic review and meta-analysis of facial botulinum toxin studies identified eyelid ptosis and brow/eyelid malposition among recognized adverse events.

Why Can Botox or Letybo Cause Eyelid Drooping?

The medication is injected into specific muscles, but botulinum toxin can affect nearby muscles if the product reaches structures outside the intended target.

The upper face contains closely interconnected muscles.

For example, treatment of the glabella can alter the balance between muscles that depress and elevate the brow.

In some patients, that can produce:

• Lowered eyebrow position
• Heavy eyelids
• Eyelid ptosis
• An altered brow shape

This is one reason that facial anatomy and injection technique are so important.

How Common Is Ptosis?

There is no single percentage that applies to every Botox or Letybo treatment.

Reported rates depend on:

• Product
• Treatment area
• Dose
• Study design
• Definition of ptosis
• Whether brow and eyelid ptosis are combined
• Follow-up duration
• Injector technique

A systematic review of aesthetic botulinum toxin studies reported upper-face blepharoptosis around 2.5% and brow ptosis around 3.1% in the studies analyzed, although these figures should not be interpreted as the expected rate for every modern treatment.

Another meta-analysis found increased risk of eyelid ptosis and heavy eyelids specifically in studies of glabellar/frown-line treatment compared with controls.

Is Eyelid Drooping Permanent?

Usually not.

When eyelid or brow ptosis occurs after cosmetic botulinum toxin treatment, it is generally temporary because the pharmacologic effect gradually wears off.

The duration varies.

A long-term study of repeated botulinum toxin treatment reported that most episodes of ptosis lasted less than three weeks, although this study involved a different botulinum toxin formulation and should not be used as a precise prediction for Letybo or Botox in an individual patient.

Patients who develop significant eyelid drooping should contact their treating medical professional rather than attempting to manage the problem themselves.

Can Letybo or Botox Cause a Droopy Brow?

Yes.

Brow ptosis is a recognized potential complication of upper-face botulinum toxin treatment.

This is different from eyelid ptosis.

A patient may describe the sensation as:

“My eyelids feel heavy.” Even when the actual problem is a lowered eyebrow.

This distinction matters because the management and expected recovery can differ.

Can Botox or Letybo Make the Face Look Uneven?

Yes, temporarily.

Facial asymmetry can occur because muscles on the two sides of the face may not respond identically. Pre-existing asymmetry may also become more noticeable after treatment.

For example:

• One eyebrow may sit higher than the other.
• One side may retain more movement.
• One side may relax more rapidly.
• A pre-existing difference may become apparent after the stronger side is treated.

This does not necessarily mean that the product itself is defective.

Can Botulinum Toxin Cause a “Frozen” Face?

It can reduce facial movement, particularly when treatment produces substantial muscle weakening.

However, the degree of movement reduction depends heavily on treatment goals and dosing. Aesthetic treatment does not have to eliminate all facial movement.

Many patients and injectors prefer a result that softens dynamic lines while preserving natural expression. This is an area where the treatment plan and injector’s aesthetic judgment are at least as important as the brand selected.

Can Letybo or Botox Cause Headaches?

Yes.

Headache is a recognized adverse effect.

The Letybo FDA label identifies headache as its most common adverse reaction, reported in 2% of patients in the clinical development program.

A meta-analysis of botulinum toxin A treatment for facial rejuvenation also found headache among the adverse events that were more likely to occur following treatment than placebo in some analyses.

A headache after treatment does not necessarily indicate a dangerous complication. However, a severe, unusual or persistent headache should be evaluated medically rather than automatically attributed to the injection.

Can Letybo or Botox Cause Bruising?

Yes.

Bruising is one of the most familiar complications of injectable aesthetic treatments. A needle can injure a small blood vessel even when the injection is performed correctly.

The likelihood can be affected by:

• Injection location
• Number of injections
• Individual anatomy
• Blood-thinning medications
• Supplements that affect platelet function
• Skin characteristics
• Injection technique

A systematic review of facial botulinum toxin treatment found localized reactions, including bruising, among reported complications.

Can Letybo or Botox Cause an Allergic Reaction?

Yes, although serious hypersensitivity reactions are uncommon.

The Letybo FDA label lists hypersensitivity to the product as a contraindication and instructs that if a hypersensitivity reaction occurs, Letybo should be discontinued and appropriate treatment initiated.

Botox Cosmetic is similarly contraindicated in individuals with known hypersensitivity to any botulinum toxin preparation or its components.

Symptoms of a serious allergic reaction can include:

• Generalized hives
• Swelling
• Difficulty breathing
• Wheezing
• Dizziness or fainting

These symptoms require urgent medical attention.

What Is the FDA Boxed Warning for Letybo?

Letybo carries a boxed warning titled:

WARNING: DISTANT SPREAD OF TOXIN EFFECT

The FDA warns that the effects of botulinum toxin may, in some circumstances, spread beyond the injection site and produce symptoms consistent with botulinum toxin activity elsewhere in the body.

Reported symptoms can include:

• Generalized weakness
• Double vision
• Drooping eyelids
• Difficulty swallowing
• Difficulty speaking
• Difficulty breathing

The FDA notes that swallowing and breathing problems can be life-threatening.

This warning is not unique to Letybo.

Does Botox Have the Same Boxed Warning?

Yes. Botox Cosmetic also carries a boxed warning concerning distant spread of toxin effect. Its FDA labeling describes possible symptoms including:

• Generalized muscle weakness
• Diplopia
• Ptosis
• Dysphagia
• Dysphonia
• Dysarthria
• Breathing difficulties

The label states that these effects have been reported hours to weeks after injection.

How Common Are Serious Systemic Complications After Cosmetic Treatment?

Serious systemic complications appear to be uncommon with cosmetic use, but their possibility is important enough that FDA labeling includes the boxed warning.

The available literature also needs to be interpreted carefully because spontaneous adverse-event reporting cannot determine the true incidence of a complication.

An analysis of FDA adverse-event reports found that serious reports were much more common in therapeutic than cosmetic cases, while cosmetic reports were predominantly nonserious. The authors also noted limitations inherent in spontaneous reporting systems.

Therefore:

Rare does not mean impossible.

Who Should Be Particularly Careful With Letybo?

The Letybo prescribing information identifies several patient groups requiring particular caution.

These include patients with:

• Neuromuscular disorders
• Compromised respiratory function
• Dysphagia
• Certain cardiovascular conditions
• Known hypersensitivity
• Infection at the proposed injection site

The FDA label specifically warns that underlying neuromuscular disorders may exacerbate the clinical effects of treatment.

A proper medical history should therefore precede treatment.

What Medications Can Interact With Letybo?

The Letybo label states that no formal drug-interaction studies have been conducted, but certain drugs may potentiate its effects.

The label specifically identifies:

• Aminoglycosides and other drugs that interfere with neuromuscular transmission
• Anticholinergic drugs
• Other botulinum neurotoxin products administered at the same time or within several months
• Muscle relaxants

The FDA recommends caution and monitoring for excessive neuromuscular weakness when these combinations are relevant.

This is one reason patients should provide their injector with a complete medication and supplement list.

Does a Higher Dose Increase Side Effects?

Potentially.

Dose is one of the variables that can influence the extent of muscle weakening and therefore the likelihood of unwanted effects.

However, there is no simple rule that:

Higher dose = side effect

or:

Lower dose = no side effect.

The appropriate dose depends on the product, indication, anatomy and treatment objective.

Importantly, using more toxins is not a strategy for achieving a better cosmetic result.

Can Injection Technique Affect Safety?

Very significantly.

Botulinum toxin treatment is both a pharmacologic treatment and a technical procedure.

The injector needs to consider:

• Anatomy
• Muscle function
• Injection location
• Depth
• Dose
• Volume
• Symmetry
• Nearby structures

A review of cosmetic botulinum toxin complications emphasized that knowledge and injection skill are important in preventing adverse effects.

A large meta-analysis of 32 randomized controlled trials involving 9,669 patients also found that injection volume was associated with treatment-related adverse events, illustrating that technical factors can matter in addition to the toxin formulation itself.

Does the Injector Matter More Than the Brand?

For many aesthetic outcomes, the answer may be yes.

That does not mean product choice is irrelevant.

It means that selecting a toxin without considering the person administering it is an incomplete safety decision.

A skilled injector should be able to assess:

• Facial anatomy
• Existing asymmetry
• Muscle activity
• Brow position
• Eyelid anatomy
• Treatment goals
• Previous toxin response
• Medical contraindications

The goal is not simply to “inject Botox” or “inject Letybo.”

The goal is to safely modify specific muscle activity while preserving an appropriate facial balance.

Dr. Monica Gavin’s Perspective

“When patients ask whether Botox or Letybo is safer, I think the more useful question is whether the treatment is appropriate for the individual patient and whether the injector understands the patient’s anatomy, muscle activity and treatment goals. Both products are botulinum toxins with established safety profiles, and both require careful patient selection and precise injection technique.”

— Monica Gavin, MD

Are Letybo Side Effects Different From Botox Side Effects?

There is substantial overlap.

Both products can produce adverse effects associated with:

• Injection
• Local muscle weakening
• Spread to nearby muscles
• Systemic botulinum toxin effects
• Hypersensitivity

The available evidence does not support presenting Letybo as having a completely different safety profile from Botox.

A 2023 network meta-analysis of several botulinum toxin type A formulations found no significant differences among the included formulations in the incidence of treatment-related or drug-related adverse events for glabellar-line treatment. Importantly, Letybo was not included in that analysis because its U.S. approval occurred later.

This is a useful example of how evidence must be interpreted carefully rather than extrapolated beyond the studied products.

What Does the Letybo Clinical Trial Tell Us About Safety?

The Phase III Letybo study enrolled 355 participants with moderate-to-severe glabellar lines. Participants received 20 Units of Letybo or placebo, and the study evaluated efficacy, onset, duration, retreatment and adverse events.

The investigators described Letybo as well tolerated.

The study also included repeat-treatment follow-up, providing more information than a single short-term injection study. However, a clinical trial of 355 people cannot detect every extremely rare adverse event.

That is why postmarketing surveillance and FDA safety reporting remain important after approval.

Does Long-Term Botox Use Cause Cumulative Side Effects?

Available long-term studies of botulinum toxin A have generally been reassuring, but they do not prove that every patient will have the same experience.

For example, a long-term study of repeated botulinum toxin treatment for glabellar lines found no evidence of cumulative adverse effects or tachyphylaxis over five treatment cycles, with adverse events generally localized and temporary.

Other repeated-treatment studies of botulinum toxin formulations have similarly reported no new major safety signal over repeated cycles.

However, Letybo is a newer U.S. product, so its accumulated postmarketing experience is naturally smaller than that of Botox.

That is a difference in evidence maturity, not proof that Letybo is unsafe.

What About Antibodies and Losing Response?

Patients sometimes worry that repeated botulinum toxin treatment will cause their body to “get used to it.” Neutralizing antibodies can theoretically reduce response to botulinum toxin.

However, clinically significant immunogenicity appears uncommon with modern aesthetic treatment. Long-term studies of other botulinum toxin A formulations have not generally demonstrated a major neutralizing-antibody problem with repeated aesthetic treatment.

Because Letybo is newer in the U.S. market, its long-term real-world immunogenicity experience is less extensive.

This is another reason not to overstate what is currently known.

What Side Effects Should Make You Call Your Provider?

Contact the treating medical practice if you experience concerning or persistent:

• Significant eyelid drooping
• Marked eyebrow asymmetry
• Significant facial weakness
• Severe or persistent headache
• Significant swelling
• Increasing redness or pain at an injection site
• Unexpected visual symptoms
• Difficulty with facial movement beyond what was discussed

Your provider can determine whether the symptom is an expected temporary effect or requires evaluation.

What Symptoms Require Immediate Medical Attention?

The FDA specifically warns patients to seek immediate medical attention for symptoms suggesting significant distant spread of toxin effect.

These include:

• Difficulty breathing
• Difficulty swallowing
• Difficulty speaking
• Significant generalized weakness
• Serious visual or neuromuscular symptoms

These symptoms are potentially serious and should not be dismissed as an ordinary cosmetic side effect.

How Can Patients Reduce Their Risk?

Patients cannot eliminate all risk, but several steps can improve safety.

1. Choose an appropriately qualified medical provider

The person administering the injection should have appropriate training and experience.

2. Disclose your medical history

Especially:

• Neuromuscular disorders
• Breathing problems
• Swallowing problems
• Previous toxin reactions
• Allergies

3. Provide a complete medication list

Include prescription medications, over-the-counter medications and relevant supplements.

4. Tell the provider about previous toxin injections

Include product and date if known.

5. Do not conceal previous complications

If you previously experienced ptosis, asymmetry or another adverse effect, tell your provider.

6. Follow post-treatment instructions

Your provider should give you specific instructions appropriate to the treatment.

7. Do not self-treat significant complications

Contact the medical practice if something unexpected occurs.

Is Letybo Safe During Pregnancy?

The available evidence is insufficient to establish safety in pregnancy.

The FDA Letybo prescribing information states that available human data from case reports are insufficient to identify a drug-associated risk of major birth defects, miscarriage or other adverse maternal or fetal outcomes.

This is not the same as proving that Letybo is unsafe in pregnancy.

It means there is insufficient evidence to establish its safety.

Pregnant patients or patients planning pregnancy should discuss cosmetic botulinum toxin treatment with their healthcare professional.

What About Breastfeeding?

The FDA label indicates that it is not known whether Letybo is present in human milk and that there are no data on the effects on the breastfed infant or milk production.

Therefore, breastfeeding patients should discuss the potential benefits and uncertainties with their healthcare professional before treatment.

What If I Have a Neuromuscular Disease?

This is an important situation requiring individualized medical assessment.

The FDA warns that pre-existing neuromuscular disorders may exacerbate the clinical effects of Letybo.

Examples of conditions that may warrant particular attention include disorders affecting neuromuscular transmission or muscle strength.

Patients should not assume that cosmetic doses are automatically safe simply because the intended treatment is small.

What If I Have Trouble Swallowing or Breathing?

This should be disclosed before treatment.

The Letybo label specifically recommends caution in patients with compromised respiratory function or dysphagia. The same principle applies to Botox: relevant medical history should be reviewed before treatment.

Is Letybo Safer for People Who Have Had Botox Side Effects?

Not necessarily.

If someone developed a complication after Botox, simply switching products does not guarantee that the complication will not recur.

For example, if a patient developed brow ptosis because of:

• Anatomy
• Injection placement
• Dose
• Muscle balance

changing from Botox to Letybo may not eliminate the underlying risk.

The provider should first determine why the complication occurred.

That is a more useful approach than assuming that changing brands solves the problem.

Is Botox Safer for Someone Who Had a Bad Reaction to Letybo?

Again, not necessarily.

If the previous reaction was a true hypersensitivity reaction to botulinum toxin or one of the product’s components, another botulinum toxin may not automatically be appropriate.

A history of a significant reaction requires medical evaluation before another botulinum toxin product is considered.

Letybo vs. Botox: What We Actually Know About Safety

The Bottom Line: Letybo vs. Botox Safety

Letybo and Botox have more similarities than differences when it comes to the types of potential adverse effects associated with botulinum toxin treatment.

Both can cause temporary local effects such as bruising and headache and can occasionally produce unwanted weakening of nearby muscles, including eyelid or eyebrow drooping. Both also carry FDA warnings concerning distant spread of toxin effect.

The available evidence does not establish that either product is universally safer.

For an individual patient, the most important safety considerations are:

The medical history + the treatment area + product-specific dosing + injection technique + injector expertise.

That is why choosing a qualified medical provider is more important than selecting a product based solely on price or marketing claims. Cost can also influence treatment decisions, but choosing a neuromodulator based solely on price may overlook factors such as the treatment area, provider expertise, dosing, and individualized treatment planning. If cost is part of your decision, see How much does Letybo cost compared with Botox? for a closer look at pricing considerations.

At Azani Medical Spa in Bethlehem, Pennsylvania, Botox and Letybo treatments should be selected based on the patient’s anatomy, treatment goals, medical history and the clinician’s assessment—not simply on which product is being promoted.

Medically Reviewed By

Monica Gavin, MD

Dr. Monica Gavin is the physician behind Azani Medical Spa in Bethlehem, Pennsylvania. She evaluates patients for aesthetic treatments including Botox and other botulinum toxin treatments, with an emphasis on individualized treatment planning, facial anatomy, safety and natural-looking results.

Medical School: Wayne State Medical School

Location: Bethlehem, Pennsylvania

About Dr. Monica Gavin

Medical References

1. FDA — Letybo Prescribing Information

LETYBO (letibotulinumtoxinA-wlbg) Prescribing Information.
U.S. Food and Drug Administration. Includes boxed warning, contraindications, warnings, adverse reactions and drug interactions.

2. FDA — Botox Cosmetic Prescribing Information

BOTOX Cosmetic (onabotulinumtoxinA) Prescribing Information.
U.S. Food and Drug Administration. Includes contraindications, boxed warning and warnings concerning distant toxin spread and lack of Unit equivalency.

3. Mueller DS, et al.

Efficacy and Safety of Letibotulinumtoxin A in the Treatment of Glabellar Lines: A Randomized, Double-Blind, Multicenter, Placebo-Controlled Phase 3 Study.
Aesthetic Surgery Journal. 2022.

4. Guo Y, et al.

Efficacy and Safety of Botulinum Toxin Type A in the Treatment of Glabellar Lines: A Meta-Analysis of Randomized, Placebo-Controlled, Double-Blind Trials.
Plastic and Reconstructive Surgery. 2015.

5. Li X, et al.

Efficacy and Safety of Botulinum Toxin Type A for Treatment of Glabellar Lines: A Network Meta-Analysis of Randomized Controlled Trials.
Aesthetic Plastic Surgery. 2023.

6. Zioga E, et al.

Safety of Botulinum Toxin A Injections for Facial Rejuvenation: A Meta-Analysis of 9,669 Patients.
Aesthetic Surgery Journal.

7. Fabi SG, et al.

Adverse Events of Botulinum Toxin Type A in Facial Rejuvenation: A Systematic Review and Meta-Analysis.

8. Cavallini M, et al.

Safety of Botulinum Toxin A in Aesthetic Treatments: A Systematic Review of Clinical Studies.
Dermatologic Surgery. 2014.

9. Wollina U.

Managing Adverse Events Associated with Botulinum Toxin Type A: A Focus on Cosmetic Procedures.

10. Recent complication review

Management of Complications Following Botulinum Toxin Facial Injections: A Narrative Review.
2026. This recent review identified upper-eyelid ptosis as the most frequently reported clinically significant facial complication in the literature reviewed through November 2025.