Understanding injections: botulinum toxin and hyaluronic acid
Botulinum toxin and hyaluronic acid play a central role in modern aesthetic medicine. These two injectable treatments are often mentioned together and sometimes confused, although their indications, mechanisms of action and objectives are very different. Understanding their differences precisely is essential to make an informed choice consistent with facial anatomy, the skin ageing process and the patient's expectations.
This article aims to provide clear, rigorous and objective information based on current scientific evidence and clinical experience.
Understanding facial ageing to choose the right treatment
Facial ageing is a complex, multifactorial and gradual process. It is not simply the appearance of superficial wrinkles, but involves several biological and anatomical mechanisms.
Over time, the skin loses elasticity and firmness as collagen, elastin and hyaluronic acid naturally present in the dermis diminish. At the same time, facial volumes change: subcutaneous fat redistributes, some compartments lose volume while others become heavier. The bone structures themselves undergo gradual resorption.
Finally, the repeated action of facial muscles responsible for expressions leads to the formation of dynamic wrinkles, which can become static over time. It is precisely on these different mechanisms that botulinum toxin and hyaluronic acid act, each in a specific way.
What is botulinum toxin and how does it work?
Botulinum toxin is a purified neurotoxin that acts at the junction between nerve and muscle. It temporarily blocks the release of acetylcholine, allowing the muscles responsible for expression lines to rest. In practice, it reduces contraction of the facial muscles attached to the skin: wrinkles smooth out because the muscle contracts less (not because the skin is “filled”).
What is hyaluronic acid and what is its role?
Hyaluronic acid is a natural component of the extracellular matrix, present in the skin, dermis and supporting tissues. In aesthetic medicine, it is used as an injectable gel with varying degrees of cross-linking to fill hollows, restore volume, hydrate the dermis and perform non-surgical facelift techniques. It does not paralyse any muscle: it acts through its volumising properties and ability to retain water.
Which wrinkles can botulinum toxin treat?
In Switzerland, botulinum toxin can be used for aesthetic purposes for the following indications:
- Temporary improvement in the appearance of moderate to marked vertical lines between the eyebrows, visible at maximum frowning (glabellar or frown lines), when these lines have a significant psychological impact in adults.
- Reduction of moderate to severe crow's feet that are clearly visible during a forced smile, when they are experienced as aesthetically troublesome.
- Treatment of moderate to significant forehead lines that appear at maximum eyebrow elevation and affect the overall facial expression.
- Relaxation of a clearly visible platysma of moderate to severe degree during maximum neck contraction, when this contraction causes significant aesthetic concern.
In these areas, the problem is not a lack of volume but repeated muscular overactivity that gradually imprints the wrinkle into the skin. By reducing the strength of contraction, botulinum toxin softens the expression (less “severe”, less “tired”) and limits the worsening of wrinkles.
Which wrinkles can hyaluronic acid treat?
Hyaluronic acid mainly treats static wrinkles and volume loss. It is indicated for:
- Nasolabial folds and marionette lines.
- Perioral wrinkles and the lip contour.
- Hollows beneath the eyes and in the tear troughs.
- Creating or restoring volume: cheekbones, lips and cheeks.
- Defining the chin, jawline or nose (non-surgical rhinoplasty).
- Facial contouring, facial feminisation or masculinisation, and non-surgical profile reshaping.
- Non-surgical facelift and facial enhancement techniques.
Here, the main problem is a loss of support (bone, fat, dermis): hyaluronic acid restores the missing volume, supports tissues and consequently smooths the skin.
Duration of results: how long do botulinum toxin and hyaluronic acid last?
Botulinum toxin has a temporary effect: muscle relaxation is reversible. Its effect generally lasts between 3 and 6 months, sometimes a little longer in certain patients or areas. As the effect wears off, muscle contraction gradually resumes; maintaining the result requires repeat injections at regular intervals.
Hyaluronic acid lasts for varying lengths of time depending on the product type, injected area and patient's metabolism. Results last an average of 6 to 12 months in mobile areas (lips, folds), and can last up to 12–15 months in certain deep or less mobile areas (cheekbones, chin, jawline) with denser gels. The product is absorbable: it gradually breaks down and can be reinjected as the effect diminishes.
The nature of the products: safety, reversibility and regulatory aspects
Botulinum toxin used in aesthetics is a standardised medical preparation available on prescription and injected within a strictly regulated setting. Aesthetic doses are very low compared with doses used in neurology, and safety is well documented when administered by a trained doctor. Its effect is reversible over time; however, if an effect is considered too pronounced, its action must be allowed to wear off.
Hyaluronic acid is a molecule naturally present in the body, synthesised for injections with different degrees of cross-linking. Products used in aesthetic medicine are absorbable and, in the event of a serious complication, an enzyme called hyaluronidase can rapidly dissolve the gel. This reversibility is an important advantage in terms of safety and psychological reassurance for the patient.
Side effects and contraindications: points to consider
For botulinum toxin, the most frequent side effects are mild: redness, small bruises, slight tenderness at the injection site and temporary headaches. Rarer complications, such as temporary eyelid ptosis, are possible and must be explained during the consultation. Contraindications include pregnancy, breastfeeding, certain neuromuscular diseases, local infections, egg allergy and combination with certain medicines.
For hyaluronic acid, common effects are also mild: swelling, redness, small bruises and temporary irregularities. More serious complications (vascular occlusion, skin necrosis, ocular injury) remain rare but require mastery of the techniques, precise knowledge of vascular anatomy and the ability to respond immediately (hyaluronidase, appropriate care). Again, pregnancy, breastfeeding, local infections and certain medical histories (hepatitis C, autoimmune diseases) are contraindications.
Natural results: can a frozen or overfilled appearance be avoided?
Correctly dosed botulinum toxin should neither completely freeze the face nor erase every expression. The aim is to reduce excessive contraction to soften features, not block all movement. The natural appearance of the result therefore depends largely on the injection plan, doses and doctor's experience.
Similarly, hyaluronic acid should not produce exaggerated volumes. A balanced result relies on reasonable quantities, a good understanding of facial proportions and an overall strategy rather than isolated filling of a wrinkle. Current research in aesthetic medicine is clearly moving towards subtle, elegant results.
Should you choose between botulinum toxin and hyaluronic acid, or combine them?
In most situations, it is not a matter of choosing “one or the other”, but of understanding what each can offer a particular face. Botulinum toxin is logical when the main problem is excessive contraction of certain muscles and overactivity in the upper third. Hyaluronic acid is preferable when correcting a hollow, restoring volume or redefining a contour.
For many patients, combining the two techniques provides more harmonious rejuvenation: botulinum toxin smooths expression lines and relaxes features, while hyaluronic acid restores facial structure and softens hollow areas. The key is to develop a coherent plan adapted to the patient's facial shape, age, lifestyle and wishes, rather than systematically applying the same pattern.
Conclusion: how do you choose between botulinum toxin and hyaluronic acid?
Botulinum toxin and hyaluronic acid are two leading treatments in modern aesthetic medicine. Their difference lies not only in composition, but in their approach to action. One acts on movement, the other on structure. One prevents and relaxes, the other fills and supports.
Understanding this distinction allows a discerning approach to aesthetic medicine, favouring suitable, gradual treatments that respect anatomy. In the hands of an experienced doctor, these techniques offer natural, lasting results that fully meet the expectations of discerning patients.
