Quick answer: Smile lines, medically known as nasolabial folds, are the creases that run from the sides of the nose to the corners of the mouth. Contrary to popular belief, they aren’t caused by smiling itself — smiling only makes existing folds more visible. The real drivers are collagen and elastin loss, descent of the cheek’s fat pads, sun damage, and genetics, and they can appear as early as your 20s and 30s in people with thinner skin or less structural support. Treatment ranges from daily sunscreen and retinoids to dermal fillers, Botox, thread lifts, and HIFU, depending on how deep the folds are and what’s causing them.
What Are Smile Lines?
Smile lines, or nasolabial folds (NLF), are the natural creases that extend from the sides of the nose down to the corners of the mouth. They’re a normal anatomical feature present on virtually everyone’s face, but they tend to become more visible and deeper with age as the underlying structures that once kept them subtle begin to change.
Smile Lines vs Marionette Lines vs Dynamic Wrinkles
It’s easy to confuse smile lines with other facial lines, but each has a distinct cause and location:
- Smile lines (nasolabial folds) run from the nose to the corners of the mouth and are largely driven by structural changes — fat pad descent, bone resorption, and collagen loss — not just muscle movement
- Marionette lines run from the corners of the mouth down toward the chin, giving a “puppet-like” downturned appearance, and are more closely tied to jawline and lower-face volume loss
- Dynamic wrinkles are lines that only appear during facial expression (like crow’s feet when smiling) and aren’t yet visible at rest — smile lines, by contrast, are usually visible even when the face is relaxed, especially as they deepen with age
What Causes Smile Lines?
A common misconception is that smiling itself “causes” nasolabial folds, or that they’re simply a sign of dry skin. In reality, research on facial anatomy shows that nasolabial folds form mainly due to structural changes beneath the skin — expression only accentuates a fold that’s already there. Muscle habits and repeated expression play a role, but they’re not the primary cause on their own.
Natural Collagen and Elastin Loss with Age
As skin ages, it produces less collagen and elastin, the proteins that give skin its firmness and bounce-back. This reduces skin’s ability to resist the pull of gravity and underlying tissue changes, making existing folds more visible over time.
Sun Exposure and UV Damage
Chronic UV exposure breaks down collagen and elastin faster than natural aging alone, a process known as photoaging. This accelerates the thinning and loss of elasticity that makes nasolabial folds more prominent, which is why sun protection is one of the most effective preventive steps available.
Repeated Facial Expressions
Smiling, laughing, and other repeated facial movements do contribute to the formation of the crease over time, since the skin folds along the same line repeatedly. However, this is a contributing factor rather than the root cause — the deeper structural changes beneath the skin matter more for how pronounced the fold ultimately becomes.
Genetics and Skin Elasticity
Some people are genetically predisposed to thinner skin, lower natural collagen density, or less robust structural support in the midface, which is why smile lines can appear noticeably even in a person’s 20s or 30s — well before the changes typically associated with aging set in. Facial shape and bone structure also play a role in how visible the fold appears at any age.
Significant Weight Loss
Rapid or significant weight loss can reduce facial fat volume, particularly in the cheeks, causing the skin to lose its underlying support and the nasolabial fold to appear deeper or more hollow. Smoking is also a well-documented contributor, since it accelerates collagen breakdown and reduces skin elasticity beyond what aging alone would cause.
How to Prevent Smile Lines from Deepening
Daily Sunscreen Use
Since UV exposure is one of the most significant accelerators of collagen breakdown, daily broad-spectrum sunscreen is widely considered the single most effective preventive step for slowing the progression of smile lines and skin aging overall.
Retinoids and Collagen-Supporting Skincare
Topical retinoids help stimulate collagen production and speed up cell turnover, which can improve skin texture and firmness over consistent use. Vitamin C serum is another well-supported option, working as an antioxidant that helps protect existing collagen from UV and environmental damage while supporting new collagen synthesis.
Hydration and Skin Elasticity Care
Well-hydrated skin appears plumper and can make fine lines less noticeable, though hydration alone won’t reverse structural volume loss. For a quick, temporary cosmetic option, some people use silicone patches over the fold area, which create a barrier that traps moisture and can temporarily soften the appearance of the line — though this is a cosmetic short-term measure rather than a lasting treatment.
Treatment Options for Smile Lines
Dermal Fillers (Hyaluronic Acid)
Hyaluronic acid fillers are one of the most common treatments for smile lines, used either to fill the fold directly or, often more effectively, to restore lost volume in the cheek area above the fold to address the underlying structural cause rather than just the crease itself.
Botulinum Toxin (Botox)
Botox is generally less central to smile line treatment than filler, since the fold isn’t purely muscle-driven, but it can be used selectively in combination with other treatments to soften the pull of nearby muscles that emphasize the fold during expression.
Thread Lift
Thread lifts use dissolvable, barbed threads inserted beneath the skin to gently lift sagging tissue, including the descended cheek fat pads that contribute to deeper nasolabial folds, offering a non-surgical lifting effect.
Laser and Skin-Tightening Treatments (HIFU)
High-Intensity Focused Ultrasound (HIFU) delivers focused energy beneath the skin’s surface to stimulate collagen production and tighten tissue over time, making it a suitable option for improving overall skin quality and mild-to-moderate sagging around the nasolabial area.
Collagen-Stimulating Injections
Beyond hyaluronic acid, injectable collagen stimulators work gradually by triggering the body’s own collagen production over several weeks to months, offering a more progressive, natural-looking improvement in skin structure and fold depth.
What to Expect During Treatment
Facial Assessment and Treatment Planning
A proper consultation starts with a full facial assessment — not just the fold itself — since treating the underlying cause (such as cheek volume loss) often improves the appearance of the fold more effectively than treating the crease in isolation.
Procedure Duration and Downtime
Most non-surgical treatments like filler or Botox take around 15 to 30 minutes and involve little to no downtime, while thread lifts and HIFU may take slightly longer and involve a short recovery period of mild swelling or tenderness.
Side Effects and Recovery
Common, generally mild side effects include temporary redness, swelling, bruising, or tenderness at the treatment site, usually resolving within a few days. More involved treatments like thread lifts may involve slightly longer recovery, with visible improvement continuing to settle over the following weeks.
How Long Do Results Last?
Results vary significantly by treatment type. Hyaluronic acid fillers typically last 6 to 18 months depending on the product and area treated, Botox effects generally last 3 to 4 months, thread lifts can provide a lifting effect for 12 to 24 months, and collagen-stimulating treatments and HIFU tend to offer more gradual, longer-lasting improvement as new collagen continues to build over several months.
Is Treatment for Smile Lines Safe?
Non-surgical treatments for smile lines are generally considered safe when performed by a qualified, trained practitioner, though — as with any injectable or energy-based treatment — they carry risks such as bruising, asymmetry, or, in rare cases, more serious complications if performed incorrectly.
Importance of a Licensed, MOH-Regulated Facility
Choosing a licensed facility regulated by the Ministry of Health is essential, since proper medical oversight significantly reduces the risk of complications and ensures the practitioner is qualified to assess facial anatomy and select the appropriate treatment approach for your specific fold pattern.
Frequently Asked Questions About Smile Lines (FAQ)
At what age do smile lines usually appear?
Smile lines can become noticeable as early as the late 20s to 30s in people with thinner skin or less structural support, though for most people they become more pronounced from the late 30s onward as collagen loss and fat pad descent progress. Genetics plays a significant role in how early they appear.
Can smile lines be removed permanently?
Not permanently through non-surgical means, since the underlying causes — collagen loss, fat pad descent, and skin aging — are ongoing processes. However, treatments like fillers, thread lifts, and collagen-stimulating injections can significantly soften their appearance for extended periods, with maintenance treatments needed to sustain results.
Is filler or Botox better for smile lines?
Filler is generally more effective for smile lines specifically, since the fold is primarily a structural and volume-related issue rather than a muscle-driven one. Botox plays a more supportive role and is more commonly used for dynamic wrinkles caused primarily by muscle movement, such as crow’s feet.
Does treatment hurt?
Most patients report only mild, brief discomfort during filler or Botox injections, often described as a quick pinch or pressure, which is typically well-tolerated and can be minimized with topical numbing cream. Thread lifts and HIFU may involve slightly more sensation but are generally manageable without general anesthesia.
Bottom Line
Smile lines (nasolabial folds) are creases that form from the nose to the corners of the mouth, often caused by natural aging, loss of collagen or repeated facial expressions. At CLEO Clinic, skin assessments are carried out under the supervision of LCP-Certified doctors to determine the best approach for softening these lines.
Each patient undergoes a thorough facial evaluation before a personalized treatment plan is advised, based on skin condition and severity of the lines, to achieve smoother, more youthful-looking skin.
