Botox side effects: risks, prevalence, and safety
Side effects of Botox are usually mild and temporary. The most common ones include redness, swelling, and a small bruise at the injection site. These typically occur in a small percentage of patients. Serious side effects are rare and are usually related to the spread of botulinum toxin to adjacent muscles.
Are the side effects of Botox dangerous? In most cases, no. The vast majority of side effects are mild and temporary. Serious side effects are rare and occur when botulinum toxin affects unintended muscles.
Author
Ville Männistö, oral and maxillofacial surgeon
Specializes in facial anatomy and disorders of the masticatory muscles, and is certified in botulinum toxin treatments. Clinical work focuses on the safe use of botulinum toxin for both aesthetic and medical indications.
Member of a research group whose study on botulinum toxin treatments for masticatory muscles has been published in an international peer-reviewed scientific journal.
View the study in the PubMed database
What are the most common side effects of Botox?
Simply put, the most common side effects are related to the injection site or local muscle effects.
Medically speaking, side effects can be divided into two main categories:
- reactions at the injection site (redness, swelling, bruising)
- symptoms related to the effects of botulinum toxin (e.g., headache, temporary muscle weakness)
The most common side effects are:
- redness at the injection site
- mild swelling
- small bruise
- mild headache
Less common are:
- drooping eyelid (ptosis)
- facial asymmetry
Surgeon's note
Side effects of Botox treatment are most often related either to the injection itself or to the local effects of botulinum toxin. This means that most symptoms are predictable and temporary.
Clinically, the most important factor is not the complete avoidance of side effects, but rather their predictability, proper dosing, and precise targeting of injections based on the individual anatomy of the face.
Is Botox dangerous?
Botox treatment performed by a doctor or dentist is a very safe procedure.
Botulinum toxin has been used in medicine for decades to treat conditions such as migraine, muscle spasms, and excessive sweating. As the drug has been in use for decades, scientifically valid data has been accumulated on its long-term effects.
The doses used in aesthetic botulinum toxin treatments are very small compared to many medical applications.
Botulinum toxin works by blocking the release of the neurotransmitter acetylcholine at nerve endings. When the nerve does not transmit the contraction signal to the muscle normally, muscle activity is temporarily reduced.
Further information on the medical use of botulinum toxin can be found, for example, on the FDA’s website.
If you’d like to learn more about how Botox treatments are performed and how safety is ensured at the clinic, check out the Botox guide on the Helsinki website.
How common are side effects from Botox?
Side effects of Botox are usually mild, localized, and temporary. Serious side effects are rare in cosmetic botulinum toxin treatments.
Most reactions associated with Botox treatments are mild and temporary.
The most common ones are:
- redness at the injection site
- mild swelling
- small bruise
- mild headache
These symptoms are usually related to the injection itself and not to the actual drug.
What is the difference between a side effect and a complication?
In short: a side effect is usually a mild and expected reaction, whereas a complication is a rarer and clearly undesirable outcome.
- Side effect: for example, a small bruise, redness, or mild swelling at the injection site
- Complications: for example, drooping eyelids, facial asymmetry, or botulinum toxin affecting the wrong muscle
Side effects of Botox treatment by frequency
- Redness and swelling at the injection site
Prevalence: very common
Duration: from a few hours to a day - Bruise
Prevalence: fairly common
Duration: approximately 3–7 days - Headache
Prevalence: fairly common
Duration: 1–2 days - Drooping eyelid (ptosis)
Prevalence: rare
Duration: weeks to months (transient) - Facial asymmetry
Prevalence: rare
Duration: transient - Allergic reaction
Prevalence: very rare
Rare side effects of Botox
In rare cases, botulinum toxin may spread to adjacent muscles.
In this case, the consequences may include, for example:
- asymmetry of the corners
- eyelid drooping
- muscle weakness in the treated area
According to several review articles, even rare complications (ptosis, muscle weakness in the injection area, asymmetry) are usually temporary.
Botox and drooping eyelids (ptosis)
One of the most well-known complications is drooping of the upper eyelid, or ptosis.
It occurs when botulinum toxin affects the levator palpebrae superioris muscle, which raises the eyelid.
The condition usually resolves on its own as the effects of botulinum toxin wear off. You can try to improve the situation with eye drops that lower intraocular pressure:
- Apraclonidine eye drops can alleviate eyelid drooping caused by botulinum toxin treatment by stimulating the levator muscle and lifting the eyelid by a few millimeters.
- The effect is temporary and serves to relieve symptoms while waiting for the botulinum toxin to wear off.
If you're wondering how to go about your daily routine after Botox treatment and what guidelines you really need to follow, see the detailed instructions: After Botox injections.
Serious side effects of Botox (rare but important)
Simply put: Serious side effects are rare but possible. They are usually caused by the spread of botulinum toxin to areas other than the target muscle.
Medically: Botulinum toxin blocks the release of acetylcholine at nerve endings. If the effect affects unintended muscles, functional disorders may occur.
Possible serious side effects include:
- difficulty swallowing (dysphagia)
- speech difficulties
- breathing difficulties
- generalized muscle weakness
These are extremely rare at the doses used in aesthetic treatments, but always require a doctor’s evaluation.
If the effects of botulinum toxin extend to the muscles involved in breathing or swallowing, this constitutes a medically significant adverse reaction that requires immediate evaluation.
Can Botox cause permanent side effects?
Based on the literature, permanent adverse effects have been observed mainly in situations where
- unofficial or counterfeit products have been used
- exceptionally high doses have been administered
- treatment has been performed by an untrained person
The consensus in the research literature is fairly unanimous. Botulinum toxin is one of the most thoroughly researched substances in aesthetic medicine, and its safety profile is very good. The drug has a local effect, the doses are small, and the effect is reversible.
How can Botox side effects be prevented?
The risk of side effects from Botox treatment can be reduced through careful treatment planning and proper injection technique.
- Treatment is provided by a trained healthcare professional: a doctor, dentist, or nurse working under their supervision.
- A professional knows the anatomy of the facial muscles in detail.
- Botulinum toxin is administered correctly.
- The patient is examined and their initial condition is carefully assessed before treatment is administered.
Most of the side effects of Botox treatments are related to the injection site, not the actual drug, i.e., botulinum toxin.
When should you contact a professional?
Most symptoms are mild. However, contact your healthcare professional if you experience
- intense pain
- visual disturbances
- difficulty swallowing
- breathing difficulties
If you have any questions, please feel free to contact me.
Can Botox go wrong?
Although botulinum treatments are safe when performed by a professional, sometimes the results are not as desired.
This may be due to botulinum spreading to the wrong muscle or an imbalance in the facial muscles.
If you would like to read more about situations where Botox has not been as successful as hoped, you can check out this article:
Frequently asked questions about the side effects of Botox
Does Botox hurt?
Botox is injected with a very thin needle. Most people experience the injections as small pinpricks. The pain is comparable to an insect bite.
How long do the side effects of Botox last?
The most common side effects, such as redness and swelling, usually disappear within a few hours. Any bruising usually disappears within 1–2 weeks.
Can Botox cause permanent damage?
The doses used in aesthetic botulinum toxin treatments are small. Any side effects are temporary. Current research evidence does not indicate that botulinum toxin used in aesthetic doses causes permanent damage.
The effect of botulinum toxin is pharmacologically designed to be temporary: nerve endings form new synapses during the months following treatment.
The effect of botulinum toxin on the neuromuscular junction is biologically reversible. Muscle function returns to normal on average 9–12 months after treatment.
On the other hand, this is precisely why botulinum treatment must be repeated every 3–6 months if the treatment results are to be maintained.
What should you not do after Botox injections?
After Botox injections, it is advisable to avoid strenuous exercise, saunas, and rubbing the injection site for the first few hours.
👉 Read more detailed instructions after Botox injections
Summary of Botox Side Effects
In short: Botox side effects are usually mild, localized, and temporary. Serious side effects are rare in cosmetic treatments.
- The most common side effects are related to the injection site (redness, swelling, bruising)
- Symptoms are usually temporary and last from a few hours to several days
- Rare side effects are related to the effect of botulinum toxin on surrounding muscles
- Serious side effects are extremely rare in cosmetic procedures
- Safety depends on proper dosing and knowledge of facial anatomy
If you are considering Botox treatment and have concerns about its safety, you can send a photo for a free assessment.
Send your photo for a free photo consultation
Botox treatments in Helsinki
If you would like to learn more about botulinum toxin treatments, you can find a comprehensive general guide here:
