8 Causes of Nasolabial Folds (Smile Lines): Prevention & Treatment Options

Cause 1Skin Aging and Loss of Firmness

UV exposure, dryness, and age-related skin changes can reduce firmness, making expression lines more likely to remain visible even when the face is relaxed.

Beneath the surface of the skin is a layer called the dermis. It contains collagen, elastin, and hyaluronic acid, which help support the skin.

Patients sometimes ask, “What is the difference between collagen and hyaluronic acid?” In simple terms, collagen forms a network of supportive fibers, while hyaluronic acid is a gel-like substance that retains water.

Over time, UV exposure, dryness, smoking, stress, and glycation-related changes can contribute to reduced skin firmness and elasticity. As the skin provides less support to the cheeks, sagging can add further shadows.

Useful everyday habits include moisturizing, sun protection, a balanced diet, sufficient sleep, and avoiding smoking. If your skin is dry or feels dehydrated, moisturizing is especially important.

For a broader guide to at-home care, see preventing nasolabial folds and caring for them at home.

Cause 2Repeated Movement of the Muscles Around the Mouth

Repeated movements when eating, talking, and smiling, combined with reduced skin elasticity, can make folds persist.

The muscles around your mouth repeatedly contract and relax as you eat and speak. Expression lines can develop in areas that move frequently. As the skin loses elasticity, some lines may remain even after the facial muscles relax.

Think of a piece of paper folded in the same place again and again. Eventually, a crease can remain even after it is opened. Facial skin is not paper, but repeated movements and changes in skin elasticity can similarly contribute to persistent creases.

Try smiling gently in front of a mirror, then relax your face and see whether the lines remain. This can help you observe their appearance, but it does not establish the cause or whether treatment is necessary.

Be cautious with facial exercises that put excessive strain on your nasolabial folds. If you feel discomfort or notice worsening, stop and reassess.

Cause 3Facial Muscle and Fat Volume

When cheek tissue forms a step over the nasolabial fold, its shadow may become more pronounced than the crease itself.

The amount and distribution of cheek muscle and fat affect how visible nasolabial folds appear. Fuller cheeks can create a contour difference around the fold, making the shadow seem deeper.

Muscles

People with strong facial muscles or a habit of moving their mouth forcefully may place greater strain on the fold when smiling. However, muscle activity should be evaluated together with skin condition and bone structure.

Fat

Fuller cheeks can create contour changes that deepen the shadow along the fold. Conversely, people with less cheek fat may still have noticeable shadows or sagging because of reduced skin firmness or underlying skeletal hollows.

Fat compartments associated with facial contours include the malar fat pad, buccal fat, and jowl fat.

Cause 4Bone Structure and Age-Related Facial Bone Changes

The shape of the bones supporting the area beside the nose, along with age-related facial bone remodeling, can affect hollows and contour differences in the upper nasolabial fold.

Natural Bone Structure

Inherited facial anatomy also affects the appearance of smile lines. For example, prominent cheekbones may create a greater contour difference that casts a visible shadow.

When the supporting area beside the nostril is naturally recessed, the upper part of the nasolabial fold may look deeper. Jaw size, tooth alignment, and other aspects of the facial skeleton can also contribute.

Age-Related Facial Bone Remodeling

The size and shape of facial bones change with age. Changes in the maxilla, which supports the area beside the nose, may make hollows near the base of the nose and upper nasolabial fold more apparent.

Bone structure is only one factor: the overlying ligaments, fat, muscles, and skin also contribute. We therefore do not recommend treatment based on bone structure alone.

Cause 5Gravity and Facial Sagging

When skin and cheek support weakens, gravity-related downward movement can accentuate contour changes and shadows.

Gravity is unavoidable. As collagen and elastin decrease and cheek support weakens, cheek tissues may descend and overlap the outer edge of the nasolabial fold.

When you look at yourself in a mirror or phone camera while lying down, your smile lines may appear less prominent than when you are standing. This happens because gravity acts differently on the cheeks, changing the contours and shadows around the folds.

However, folds appearing softer when lying down does not prove that sagging is the only cause. Existing skin creases and hollows beside the nose also need to be considered.

Cause 6Rapid Weight Loss

A quick reduction in cheek fat can make hollows or sagging more noticeable, depending on your skin firmness and underlying facial structure.

Rapid weight loss may make nasolabial folds stand out. When cheek fat decreases over a short period, the skin may temporarily appear looser or more wrinkled as the facial contour changes.

This may be especially noticeable in people who already have reduced skin elasticity. On the other hand, reducing cheek fat may soften shadows in people with fuller cheeks. Results vary from person to person.

Cause 7Changes After Fat-Dissolving Injections or Liposuction

After reducing cheek fat, the balance between the amount removed and the skin’s firmness can sometimes make sagging or wrinkles more noticeable.

Some patients notice more pronounced nasolabial folds or wrinkles after fat-dissolving injections or facial liposuction. Reduced fat may reveal pre-existing skin laxity or sagging. This is a particular consideration in patients over 40, when age-related laxity may be more common.

However, the outcome depends not only on age but also on the treated area, the amount of fat removed, the original facial volume, skin condition, and bone structure. Before pursuing cheek-fat reduction, consider the potential for future hollowness or sagging as well as facial slimming.

Cause 8Changes Around the Mouth After Dental or Oral Surgery

If your facial appearance changes after orthodontics, tooth extraction, or jaw surgery, consider not only the procedure but also facial anatomy, weight changes, expressions, and aging.

Some patients start noticing their nasolabial folds after dental procedures, particularly orthodontic treatment, extractions, or jaw surgery.

Surgery that changes bone structure may significantly alter facial contours. In contrast, orthodontics or tooth extraction alone does not necessarily cause major changes in facial bones. Weight changes during treatment, mouth habits, chewing patterns, expressions, and aging may also play a role.