What causes wrinkles
known as smile lines ?
Smile lines initially deepen through repeated facial expressions, particularly smiling, then become established as the skin loses elastin and collagen fibres over time. However, certain factors accelerate their development.
Skin characteristics play a decisive role. Thin, dry or dehydrated skin creases more readily because it has less support and recovers less effectively after facial movements. Conversely, thicker, better-lubricated skin is more resistant to wrinkle formation.
Lifestyle also influences skin condition. Smoking, alcohol, lack of sleep and chronic stress impair skin quality and accelerate ageing. External aggressors — sun exposure, pollution and hormonal changes — further weaken skin tissue by generating oxidative stress.
Maintaining hydration, protecting the skin from UV rays and adopting a balanced lifestyle help slow the development of these wrinkles.
The different types of smile lines : location and characteristics
Smile lines do not all have the same causes or occur in the same locations. Some result from tissue sagging, others from repeated expressions or mechanical skin compression.
Nasolabial folds, located between the side of the nose and the mouth corner, deepen over time because of midface tissue descent and loss of bone and ligament support. They give the face a tired appearance.
Marionette lines, which extend downwards from the mouth corners, pull these corners down and can create a sad appearance.
Perioral fine lines, often vertical, occur above the upper lip. They are caused by repeated orbicularis oris movements (speaking, smiling, smoking) and accentuated by thin skin, smoking and photoageing.
Crow's feet, at the outer eye corners, appear when smiling through contraction of the orbicularis oculi muscle. Initially dynamic, they become permanent as the skin loses elasticity.
Fine cheek wrinkles result from repeated skin compression when smiling. When the skin always folds in the same places and its recovery capacity declines, wrinkles become permanent.
Smile lines do not all share the same cause : some arise from facial volume loss, others from natural skin laxity, repeated smiling movements or skin creasing. Since each wrinkle forms differently, there is no single treatment. Care must therefore be personalised, combining several techniques to address all the underlying mechanisms.
Why do smile lines appear with age ?
Over time, collagen and elastin fibres deteriorate, reducing skin elasticity. The dermis becomes thinner and less hydrated, losing its ability to withstand pressure or recover its original shape after facial expressions. Subcutaneous fat, particularly in the cheekbone and cheek areas, gradually diminishes. This causes facial tissues to slide downwards, accentuating nasolabial folds and marionette lines. Meanwhile, repeated contractions of the smiling muscles, the zygomatic muscles and orbicularis oris progressively mark the skin surface. Skin ageing is therefore both structural and dynamic, justifying a multidimensional treatment strategy.
Diagnosing smile lines :
the medical assessment before
treatment
The medical assessment of smile lines begins with observation of the face at rest and during movement. Dr Romano analyses skin quality, thickness, elasticity and signs of photoageing. The doctor observes muscle dynamics and the strength of muscle contractions . Volume assessment is essential, as smile lines are often worsened by loss of structural support in the cheeks, cheekbones or chin. Diagnosis must consider the entire middle and lower thirds of the face to propose harmonious treatment that respects each face's individuality.
Smile line treatment : which options for each cause ?
Smile lines develop through several mechanisms. Treatment therefore relies on a precise assessment of their cause.
Depending on the clinical examination, several treatments may be offered, alone or in combination :
- Hyaluronic acid : recommended when wrinkles are present at rest or associated with loss of tissue support. Depending on individual needs, injections restore volume, support lax tissues through medical lifting techniques or, for certain indications, treat specific folds directly (by injecting the fold itself).
- Skinboosters : these injections of lightly cross-linked hyaluronic acid improve deep skin hydration, suppleness and quality, particularly when fine lines are associated with thin or dehydrated skin.
- Collagen biostimulators : indicated for loss of firmness, they gradually stimulate natural collagen production and achieve lasting improvements in skin quality.
- Fractional laser : this treatment remodels the dermis to increase skin density and improve superficial fine lines and mild to moderate skin laxity.
In most cases, combining several techniques achieves a more harmonious result than a single treatment. The choice depends on the patient's anatomy, wrinkle severity, skin quality and expectations expressed during consultation.
How can the development of
smile lines be prevented ?
Although smile lines are partly inevitable, certain measures can slow their development and reduce their appearance. The first step is to preserve skin quality with appropriate skincare. Well-hydrated, supple and elastic skin wrinkles less readily. Products containing hyaluronic acid or restructuring agents help maintain good hydration and strengthen the dermis, particularly as the skin begins to thin.
Hydration is not limited to skincare application, as internal hydration is also important. Regular water intake promotes skin balance, supports cellular functions and improves the skin's ability to regenerate.
Sun protection is another essential element. UV radiation accelerates collagen and elastin breakdown, weakens the skin and encourages wrinkles around the mouth and eyes. Even in cloudy weather, sunscreen helps delay skin ageing.
A healthy lifestyle also helps preserve skin quality : avoiding smoking, limiting stress, getting restorative sleep and eating a diet rich in antioxidants contribute to wrinkle prevention.
Finally, practices such as massage or gentle facial movement exercises can improve circulation, stimulate skin tissues and help the skin recover after movement.
Smile lines are part of natural facial ageing, but strengthening skin quality and protecting skin structures can reduce their formation and delay their becoming established.
Smile line treatment prices
In Geneva, a hyaluronic acid injection for smile lines costs 600 CHF per syringe, a Skinbooster costs 400 CHF per syringe and a fractional ablative laser starts from 600 CHF per session.
A study analysed facial movements in three dimensions in thirty women treated with hyaluronic acid for nasolabial folds and marionette lines. At forty-two days, maximum stretching of these regions during expressions had decreased, becoming closer to the pattern of a younger untreated group. These observations show the value of assessing smile lines in motion, rather than relying only on photographs taken at rest.
A pilot study involving thirty women assessed how natural facial expressions looked after correction of nasolabial folds and marionette lines with hyaluronic acid. At forty-two days, the naturalness of expressions in motion was at least preserved in all participants, alongside improved folds and high satisfaction. These results concern the flexible gels and technique studied, in an open-label study.
A randomised study involving sixty patients compared two hyaluronic acid injection protocols that differed in the order in which the chin, nasolabial folds and marionette lines were treated. At nine weeks, an aesthetic improvement was observed in all patients in both groups, according to the assessment scale used. Satisfaction was high and results were considered natural. These observations concern treatment of several areas of the lower third of the face, rather than an individual smile line.
Frequently asked questions
What are smile lines ?
These are wrinkles that form at the corners of the eyes, on the cheeks or around the mouth when smiling. Over time, some remain visible at rest.
Can smile lines be treated while keeping a natural smile ?
Yes, the aim is to soften wrinkles without interfering with the smile. The doctor adapts treatment to the muscles and volumes of the face. The goal is not to erase every crease that appears when smiling.
Why do smile lines remain visible at rest ?
Over time, repeated movements, skin ageing, sun exposure and loss of facial volume can cause these wrinkles to become established.
Which treatment should I choose for smile lines: botulinum toxin or hyaluronic acid ?
The choice depends on the area and the cause of the wrinkles. Botulinum toxin reduces the contractions responsible for crow’s feet. Hyaluronic acid fills certain creases and corrects volume loss.
Can creams soften smile lines ?
Moisturising creams can soften fine lines caused by a lack of hydration. They cannot fill a deep wrinkle or restore lost volume.
What are the risks of injections for smile lines ?
Injections may cause bruising, swelling or asymmetry. Botulinum toxin can alter the smile if it weakens a muscle involved in its movement. In rare cases, hyaluronic acid can block a blood vessel and damage the skin.
