Smile lines at 20, or even at 15, are usually normal. The fold between the nose and mouth is part of facial anatomy, and full cheeks and strong lip-lifting muscles make it show clearly when you smile. Lines that stay deep at rest at a young age often reflect face shape, genetics, weight change, sun or smoking, not early aging.
This article is part of our smile lines overview. It answers the questions younger readers ask most.
Causes
Common smile lines around mouth causes include anatomy, muscle pull, cheek fullness, sun, smoking, genetics and later the natural loss of skin elasticity.
A 2024 anatomy review in Diagnostics explains that the skin below the fold is firmly attached to the muscle around the mouth, while the cheek above is looser. Muscles that lift the upper lip also pull on the skin near the fold when you smile. That’s why everyone has a fold.
Mayo Clinic lists the factors that turn expression lines into lasting ones: age-related loss of elasticity and collagen, ultraviolet light, smoking, pollution, repeated expressions and family history. In a 2013 study of 79 identical twin pairs, smokers had deeper nasolabial folds than their twins, and visible differences appeared with as little as five years’ difference in smoking.
Young age
Early smile lines in teens and twenties are usually from full cheeks and expressive muscles, which is normal and often looks youthful.
The same review notes that in youth these lines may be prominently visible only during smiling. Fuller cheeks bunch up more when you smile, so smile lines on young people can look deeper than in an older, slimmer face. At 15, smile lines are almost always this kind of expression fold.
When smile lines at a young age stay at rest, they can come from:
- Inherited face shape, such as a flatter area beside the nostril.
- Weight loss that empties the cheeks.
- Regular sun exposure without sunscreen.
- Smoking or vaping.
In my practice, I usually advise people under 25 against filler for smile lines that only show when they smile. Sun protection is the better investment at that age.
When smiling vs not smiling
Having smile lines when smiling is normal at every age; smile lines when not smiling suggest volume loss, sagging or skin changes.
| What you see | Likely meaning | Action |
|---|---|---|
| Lines only while smiling | Normal muscle pull | Sunscreen; no treatment needed |
| Faint lines without smiling | Early skin change or face shape | Sunscreen, retinoid, no smoking |
| Deep fold at rest | Volume loss or sagging | Medical assessment |
People compare smile lines vs no smile lines in photos, but a face with no fold at all is rare and usually reflects lighting or editing.
Dehydration lines
Comparing smile lines vs dehydration lines: dehydration lines are fine, criss-cross surface lines that improve with moisture, while folds don’t.
Mayo Clinic notes that dry skin can cause fine lines and that moisturising daily helps trap water in the skin. If fine lines beside the mouth fade after a few days of moisturiser, they were dryness lines. A fold that stays the same needs a different approach; see our guide on how to get rid of smile lines or skincare for smile lines.
Frequently Asked Questions
FAQ
Short answers on smile lines at a young age, what causes them around the mouth and whether to treat them early.
Is it normal to have smile lines at 20?
Yes. This crease is normal anatomy, and full cheeks plus active lip muscles make it show when you smile. It isn’t a sign of early aging unless the fold stays deep at rest and keeps deepening.
Why do I have smile lines at 15?
Most teens with visible smile lines have full cheeks and expressive faces. It shows when they smile and fades at rest. Genetics and face shape play a part. Daily sunscreen is the most useful habit to start now.
What causes smile lines around the mouth?
The skin under the fold is firmly attached to the mouth muscle, while the cheek above is looser. Over time, lost elasticity, sun damage, smoking, weight changes and genetics deepen the crease, according to Mayo Clinic and a 2024 anatomy review.
Should I get filler for smile lines in my twenties?
Usually not for lines that only show when you smile. Filler can make a young face look heavy, and US-approved fillers are for adults 22 and over. If a fold is deep at rest because of face shape, a doctor can assess whether small, careful treatment would help.
Can smiling less prevent smile lines?
It isn’t worth trying. Repeated expressions play a part, but sun protection, not smoking and a stable weight matter more. Smiling is part of a natural, healthy-looking face, and the fold is there anyway.
Do smile lines go away on their own?
Lines that only appear when smiling fade as soon as you relax. Dehydration lines can fade with moisturiser. A fold that is visible at rest doesn’t disappear on its own, though skincare can improve surface lines over months.
If you’d like to know whether your smile lines need any treatment, you can book a consultation with Metropole Clinic by ABmedi. For types and treatments, return to the smile lines hub.
This article is for general education and does not replace a personal medical consultation.
References
Show sources
- Hong GW, Song S, Park SY, et al. Why Do Nasolabial Folds Appear? Exploring the Anatomical Perspectives and the Role of Thread-Based Interventions. Diagnostics. 2024;14(7):716. mdpi.com
- Wrinkles: Symptoms and causes. Mayo Clinic. 2023. mayoclinic.org
- Face it: Twins who smoke look older, says study in Plastic and Reconstructive Surgery. Newswise. 2013. newswise.com
- Kafi R, Kwak HSR, Schumacher WE, et al. Improvement of naturally aged skin with vitamin A (retinol). Arch Dermatol. 2007;143(5):606-612. pure.johnshopkins.edu
- Dermal Fillers (Soft Tissue Fillers). US Food and Drug Administration. fda.gov
