What's the difference between botulinum toxin and hyaluronic acid?
In aesthetic medicine, two injectable treatments play a major role: botulinum toxin (often called « Botox® ») and hyaluronic acid (or fillers). Although both are used to reduce the signs of aging without surgery, their actions, targeted areas, duration of effects, and indications differ completely. This article explains in detail why they are not interchangeable — but complementary — and how to choose according to your needs.
1. Origins and mechanisms of action
Botulinum Toxin (Botox)
Botulinum toxin is a bacterial toxin (Clostridium botulinum) which, in very small doses, acts as a muscle relaxant by blocking nerve signals to targeted muscles. In aesthetic medicine, this helps reduce expression lines, caused by repeated muscle contractions, such as those on the forehead, frown lines, or crow's feet.
Hyaluronic Acid
Hyaluronic acid is a naturally occurring molecule in the body (dermis, cartilage, eyes). It is known for its hydrating and volumizing properties, capable of retaining up to 1000 times its weight in water. When injected, it is used as a filler to smooth static wrinkles, restore volume, or reshape facial contours.
2. Areas and types of wrinkles treated
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Botulinum toxin: targeting dynamic wrinkles, it is particularly effective on the upper third of the face (forehead, between the eyebrows, around the eyes).
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Hyaluronic acid: suited for static wrinkles and volume loss, it is often injected into the middle and lower third of the face — nasolabial folds, cheekbones, lips, jawline.
3. Duration of results
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Botulinum toxin: effects appear within a few days (2 to 8 days) and last approximately 3 to 6 months.
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Hyaluronic acid: effects are immediately visible. Their duration varies depending on the concentration — between 6 months and 2 years (or even longer depending on the product, especially cross-linked forms).
4. Side effects and precautions
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Botulinum toxin: rare but possible side effects — bruising, headaches, temporary ptosis (drooping eyelids), especially if improperly administered.
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Hyaluronic acid: generally well-tolerated, except for localized redness, swelling, or bruising. In case of issues, hyaluronidase can be used to dissolve the acid.
5. Complementary use and medical indications
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Complementary: the two treatments can definitely be combined. The toxin relaxes muscles in the upper face, while hyaluronic acid restores volume elsewhere for a natural overall effect.
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Other medical uses:
6. In summary: a comparison table
| Criterion | Botulinum Toxin (Botox) | Hyaluronic Acid (Fillers) |
|---|---|---|
| Mechanism | Relaxes muscles | Fills / hydrates / restructures |
| Targeted areas | Upper third (forehead, eye contour, frown lines) | Middle and lower third (cheeks, folds, lips, jawline) |
| Effects | Smoothing of expression lines | Volume, hydration, filling of static wrinkles |
| Onset of efficacy | 2 to 8 days | Immediate |
| Duration | 3 to 6 months | 6 months to 2 years (or longer depending on formulation) |
| Side effects | Bruising, ptosis, headaches (rare) | Redness, swelling, possibility of dissolving with hyaluronidase |
| Other uses | Hyperhidrosis, spasms, migraines | Ophthalmology, osteoarthritis, hydration, dry eyes |
Thus, botulinum toxin and hyaluronic acid are two powerful allies in aesthetic medicine, but with different uses: one smooths dynamic wrinkles, while the other restores volume and structure. When carefully chosen and combined by skilled professionals, they allow for natural and harmonious facial rejuvenation.