What Are the Side Effects of Botox Injections?

Does Botox have any side effects - from our Surrey Clinic

Botox has one of the strongest safety records of any procedure in aesthetic medicine. But no treatment is entirely without side effects, and patients deserve an honest account of what can occasionally occur.

Here we address side-effects but you might also want to read is Botox safe?

Here is are my thoughts with, I hope rather more candour than the average patient information leaflet.

Mild side effects — common and short-lived

The most frequent side effects are minor and resolve within hours. A small amount of swelling at the injection sites is almost universal, simply from the tiny volume of fluid injected. Some redness is equally common. Both are gone well before the end of the day.

Bruising is less predictable. It is more common around the crow's feet area than on the forehead, but can occur anywhere. When it does, it is a nuisance rather than a concern, and resolves on its own within a few days.

Two side effects are worth a particular mention because they are not always well explained.

The first is a perception of numbness. When the muscles in the treated area stop moving, some patients interpret that unfamiliar stillness as numbness — a feeling that the skin has lost sensation. It has not; skin sensation is entirely unaffected by botulinum toxin. The feeling usually passes within a couple of days as patients adjust to their new normal.

The second is headache, or what patients describe as headache. In my experience, it is less a true headache and more that same sensation of heaviness or unusual stillness, interpreted through a different frame. It is mild and short-lived, typically lasting a day or so.

After a Botox treatment your follow-up appointment is an important time to review your results.

Moderate side effects — less common, still worth knowing

Brow drop

This is where the brow position sits lower than intended. It is the most common of the moderate side effects and one I have written about separately in the context of patients who have tried Botox once and not liked the result. It is technique-dependent and dose-dependent, and in experienced hands is uncommon. Read why you might have not liked Botox.

Brow elevation

The opposite problem is excessive brow elevation, sometimes called the Spock effect. This occurs when the central forehead is overtreated relative to the outer brow, causing an arched or quizzical appearance. Again, it is a question of distribution and dose, and is correctable. For many women a small degree of brow lift can be desirable. This is something we would discuss at your consultation, which we believe to be an important part of your treatment.

For many women a small degree of brow lift can be desirable.

Brow heaviness

Some patients experience a perception of heaviness even when the brow position is anatomically normal. The brow is exactly where it should be, but the reduced muscle activity produces a sensation that some patients find takes adjustment. This is not a complication in the clinical sense, the result may be entirely appropriate, but it is worth discussing in advance with patients who are particularly sensitive to that feeling.

More significant side effects - rare but important - eyelid droop

Upper eyelid droop, known clinically as lid ptosis, is the side effect that warrants the most thorough explanation. It occurs when Botox injected into the outer part of the frown muscle spreads downward and affects the muscle responsible for lifting the upper eyelid. The result is a drooping of one or both eyelids that is, understandably, distressing and inconvenient for the patient.

It is often cited as more common with inexperienced injectors, and technique certainly matters. But I think it is important to be honest: it can happen to any injector, including very experienced ones. At The Cosmetic Doctors Company, we have not seen a case in well over ten years. That is a record I am proud of, but I would not use it to suggest the risk is zero; only that careful technique and conservative dosing reduce it substantially.

When it does occur, apraclonidine eye drops (Iopidine) provide meaningful symptomatic relief by stimulating a small compensatory muscle in the lid. Full resolution, however, only comes as the botulinum toxin wears off.

An important point to remember

Which brings me to what I consider the single most important thing to understand about all Botox side effects: every one of them always resolves completely as the treatment wears off. There are no permanent consequences.

Systemic side effects — exceedingly rare in licensed cosmetic use

Flu-like symptoms are sometimes listed as a possible side effect of botulinum toxin. In the many thousands of treatments I have been involved with over the years, I have never encountered this. I mention it only because patients sometimes read about it and worry.

More serious systemic effects such as muscle weakness, vision disturbance, difficulty swallowing or speaking, and breathing problems — are listed in prescribing information and deserve acknowledgment. In my clinical view, these are exceedingly rare consequences of licensed botulinum toxin used at recommended cosmetic doses.

Where they have occurred, the association has generally been with unlicensed or counterfeit products. I have written about the risks of unlicensed or fake Botox separately, and I would direct anyone with concerns here Fake Botox Is a Reality. And It Could Happen to You.

True allergy and anaphylaxis with Botox is exceedingly rare

True allergy following botulinum toxin injection is, in the medical literature, extraordinarily uncommon. A comprehensive review published on PubMed Central‍ ‍identifies only three case reports widely accepted by the medical community as likely representing genuine anaphylaxis caused by the botulinum toxin product itself. Given that tens of millions of doses have been administered worldwide over more than thirty years, that is a reassuring figure and one that puts the theoretical allergy risk in its proper perspective.

Reference:

Hypersensitivity Reactions Associated With Aesthetic Botulinum Toxin A Injections: A Case Series. Buchholz E et al.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12665379/

About the author

Dr Peter Forrester is Medical Director of The Cosmetic Doctors Company in Esher, Surrey. He has practised aesthetic medicine for over 25 years and has extensive experience in non-surgical facial rejuvenation. He believes that all good aesthetic treatment begins with a thorough consultation, honest advice and a commitment to providing safe, natural-looking results for every patient.