What causes smile lines, and how can they be prevented?

Doctor's Answers (2)

Smile lines/ laugh lines - or medically known as nasolabial folds (NLF) - are slightly curved, downwards sloping lines that extend from the sides of the nose down to the corners of the mouth. It is a natural occurrence, even in the very young, and usually worsens as we age.

The anatomical basis for NLF is due to the attachments of our cheek facial muscles to the corners of the mouth, which enables us to smile - thus the colloquial name of smile lines. To prevent it totally is near impossible, unless one can stop smiling or do any facial movements that move the corners of the mouth upwards. 

It can, however, be lessened, or treated if it's already present. Various aspects of ageing do cause the NLF to worsen over time. Different layers of the face, from the topmost skin to the bottom-most bone, all contribute to the appearance of the NLF.

The skin undergoes repetitive creasing as we move our face, and like a piece of paper folded over a thousand times, the line can eventually set into the skin. This is more apparent with age as our skin collagen degrades. Such skin creases can be lessen with various measures/ treatments. Home treatments include using skin care that contains ingredients that stimulate our skin to regenerate, e.g. retinols/ retinoids. Hydrating ingredients is important as well, as dehydration makes every line/ wrinkle on our face appear more apparent. Treatments include injectables e.g. very fluid fillers to plump up the skin with hyaluronic acid, and regenerating substances (Rejuran, NCTF-135HA). 

The sagging of fats downwards with age is another important factor that aggravates the NLF. Some have naturally heavier cheek fats, and their NLF are apparent even when young. For those who experience sagging with time, may consider lifting the sagging fats with machine-based heat treatments e.g. HIFU, radiofrequency; accurate filler placement on the cheeks may also achieve some lifting effects; those more accustomed to aesthetic treatments may even opt for thread-lifting. Another option is to camouflage the difference in depth between the overhanging cheek fats and NLF using fillers.

Facial muscles are naturally strong in some, and as such, NLF may appear earlier in those. Botox can be used to relax those muscles, especially in those with gummy smile (excessive show of gums when smiling). Caution must be exercised if botox is used, as those facial muscles around the mouth have a complex intertwining relationship, and any wrong placement may results in an asymmetrical appearance of the mouth.

Bone loss is another contributing factor for the appearance of NLF. As we age, the maxillary bone also shrinks, and without a proper base underneath the NLF, the depth of the NLF becomes more apparent. The maxillary bone is also related to our dentition, and as such, any dental procedures that alter the placement of our teeth can also affect various aesthetic features around the mouth - NLF, lips. For those with features of bone resorption, thick fillers can be placed deep to mimic the original bone, thus supporting the soft tissues above, reducing the appearance of the NLF.

As implied above, the cause for the NLF varies among different individuals, and the best result is obtained with an individualized treatment after consultation with your doctor.

Dr Chin Yee Choong

"Dedicated to the ethical practice of Aesthetic Medicine"


Smile lines are also known as dynamic wrinkles that are caused by the over-activity of the muscles of facial expressions.

Depending on the location of smile lines and the underlying facial muscles that cause it, Botox may help to reduce its appearance. For example, crow’s feet are smile lines that may be greatly reduced by the Botox injection to the corners of the eyes.

A full assessment by your preferred aesthetic doctor will be the first step to take to determine if Botox will help. Creams and laser treatments are unlikely to help in this instance.

Hope this helps!

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