The frown line, or glabellar wrinkle, is one of the first expression lines to appear on the face. Resulting from the repeated contraction of the corrugator and procerus muscles — particularly engaged when frowning — it gives the eyes an expression sometimes perceived as severe, tense, or worried.
The reference treatment to smooth this wrinkle is an injection of type A botulinum toxin, commonly called Botox®. This medication works by temporarily relaxing the muscles responsible for the wrinkle. One of the aspects most frequently discussed by patients during consultations is the duration of this treatment : how long will the effects of Botox last, and when should a new session be considered ?
Botulinum toxin works by blocking the release of acetylcholine, a neurotransmitter essential for voluntary muscle contraction. When injected in very small doses into the glabellar muscles, it causes a targeted reduction of muscle activity, allowing the skin to relax on the surface and the wrinkle to gradually fade.
The effect does not appear immediately : it generally takes three to five days to observe the first signs of relaxation, with maximal effectiveness reached between the 10ᵗʰ and 14ᵗʰ day. Subsequently, the muscle remains partially or completely inactive for several weeks, until the nerve endings regenerate. It is this neuromuscular reconnection that determines the duration of the therapeutic effect.
In the majority of patients, the visible effects of Botox injections on the frown line last between 4 and 6 months. However, there are significant individual variations, related to several factors :
Under optimal conditions, the result lasts on average five months, with sometimes residual effects up to six or seven months, particularly in patients who regularly repeat the injections.
In the weeks following the injection, the effect of the toxin gradually diminishes. The resumption of muscle activity does not occur abruptly, but through a gradual recovery of mobility. In practice :
In many cases, however, the wrinkle never returns to its initial depth, thanks to the muscle weakening achieved over successive sessions.
While the duration of the toxin’s action is largely determined by biological factors, it is possible to adopt certain strategies to optimize its longevity :
Conversely, injecting a higher dose does not prolong the duration of the treatment. Overdosing only increases the risk of adverse effects, without additional benefit on the longevity of the results.
When the action of Botox wears off, the nerve endings gradually resume their function, and the muscles regain their initial tone. In patients who do not repeat the treatment, the frown line eventually reappears, within a timeframe that varies depending on the initial skin condition.
It is important to note that Botox never worsens a wrinkle. On the contrary, it allows the area to rest for several months, thereby slowing its progression. Patients who stop treatment will regain their natural expression, without deterioration due to rebound effects.
Yes. Several clinical studies have shown that when a muscle is kept at rest for several consecutive years, its tone decreases. It partially atrophies, leading to weaker contraction and therefore a less pronounced wrinkle, even outside the active treatment periods.
Some patients, after 3 or 4 years of regular treatment, can thus space sessions to once every 7 to 8 months, while maintaining a good aesthetic result. This phenomenon, called muscle deconditioning, is particularly observed in the treatment of the glabella, where reflex contractions are very frequent.
The duration of action is not the same for all patients; there are significant individual variations, influenced by several factors :
It is therefore essential to adapt the protocol to each patient, rather than relying on a theoretical average.
The glabella, located between the eyebrows, is a highly active muscular area. It contracts frequently, often unconsciously, whether at rest, under stress, while concentrating, or even when reading. This almost constant activity explains the early and pronounced appearance of wrinkles in this region.
This is also why Botox is particularly effective in this area. However, due to this muscular hyperactivity, its effect may last slightly less than in other areas of the face. The glabella is therefore an area with high muscle reversibility, requiring a strict maintenance protocol to sustainably preserve the smoothing effect.
Yes. Although the various type A botulinum toxins (Botox®, Azzalure®, Bocouture®, Xeomin®, etc.) share a common mechanism of action, they differ in molecular structure, protein weight, tissue diffusion, and stability. These differences can, marginally, influence the duration of action.
For example, some studies have suggested that Azzalure®, due to its protein composition and more targeted diffusion, could offer a slightly longer duration of effect compared to certain alternatives. Bocouture®, on the other hand, is often preferred for its purity but may have a slightly shorter action in some patients. These variations remain moderate, but an experienced physician will know how to choose the toxin best suited to the patient’s muscle profile, aesthetic goal, and desired session frequency.
Botulinum toxin acts as a temporary inhibitor of neuromuscular transmission. After injection, it prevents the release of acetylcholine, thereby blocking the contraction command of the target muscles. However, this inhibition does not irreversibly damage the nerves or muscle fibers.
The peripheral nervous system has a regenerative capacity : over the weeks, new synaptic junctions form, gradually restoring motor function. It is this neuromuscular recovery mechanism that explains the transient nature of Botox effects. Botulinum toxin injections follow a logic of controlled repetition, providing the possibility to adjust doses and the therapeutic strategy at each session.
The disappearance of Botox effects occurs gradually, never suddenly. The first sign is often a slight return of mobility in the glabella : the patient then notices a small frown when expressing an emotion or concentrating. This change sometimes goes unnoticed, as the wrinkle remains subtle at rest.
Over time, muscle contractions gain intensity, and the skin begins to wrinkle again. If no new injection is performed, the frown line eventually becomes visibly apparent. Its appearance may return to the initial state or seem slightly softened, depending on skin quality and the regularity of previous treatments.
The duration of results from hyaluronic acid injections for the frown line generally ranges between 10 and 18 months, depending on several intrinsic and extrinsic factors. The hyaluronic acid used to fill this wrinkle is often slightly cross-linked, meaning it is stabilized to resist the body’s natural enzymatic degradation. However, this duration remains indicative : it depends on the mobility of the treated area, the type of acid used, the depth of the wrinkle, and the patient’s metabolism.The glabella being a region highly involved in facial expressions — particularly frowning — the injected product is subjected to constant mechanical stress, which can accelerate its resorption. In younger patients or those treated preventively, the effect may last longer, whereas in patients with a pronounced static wrinkle, a maintenance session every 9 to 10 months is often recommended to maintain optimal results. Finally, when hyaluronic acid injection is performed in synergy with a prior botulinum toxin injection, the duration of the filling can be significantly prolonged, as the gel undergoes less daily muscular tension.
Article written by Dr Romano Valeria
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