Fine lines — first separate expression from dermis
Fine lines are not one condition. Lines that appear only with expression and vanish when the face relaxes, and lines that have settled in regardless of expression, have different causes and different answers. Mixing the two misdirects the choice of treatment. And addressing lines alone leaves about half behind — in an assessment of 112 Korean women, wrinkles contributed 37%, sagging 37% and pigmentation 26% to perceived age.
The short answer
Fine lines are not one condition; they divide broadly into two. Lines that appear only with expression and vanish when the face relaxes are mainly caused by muscle action, while lines that have settled in regardless of expression are mainly caused by a thinning dermis and reduced collagen. Mixing the two misdirects the choice of treatment — repeating a muscle-directed approach on a line that settled in because the dermis thinned will not bring the change wanted, and repeating boosters on an expression line does the same in reverse. And addressing lines alone leaves about half behind. In a study where 92 assessors rated 112 Korean women (Flament 2021), the contribution to perceived age split as wrinkles 37%, sagging 37% and pigmentation 26% — effectively a tie. That is why erasing wrinkles can leave the face looking the same age.
The two kinds of fine lines
| Aspect | Expression lines | Settled lines |
|---|---|---|
| When they show | When smiling or frowning | Always, regardless of expression |
| What causes them | Repeated action of facial muscles | Loss of dermal collagen; a thinning dermis |
| Direction that fits | Reducing muscle action | Collagen boosters and other dermis-directed treatments |
| How to tell | Whether it disappears when the face relaxes | Whether it is visible in a photograph with no expression |
The check in the mirror is simple — face forward with no expression, and if the line is still there, it belongs to the dermis side.
What is not the answer
“Botulinum toxin smooths every fine line.” Lines that have settled in regardless of expression remain even when muscle action is reduced, because muscle action is not what caused them. And too much makes the expression itself look unnatural.
“Moisturising makes fine lines go away.” It is true that dryness makes fine lines stand out more. But standing out and having settled in are different problems. The barrier side is set out in the skin barrier.
“Erase the lines and you look younger.” In Flament 2021 the contributions split as wrinkles 37%, sagging 37% and pigmentation 26%. Fink & Matts 2008 points the other way: removing surface topography took 10.84 years off, while removing colour alone took off 1.05 years. In other words, the received wisdom that firmness matters more than wrinkles holds in only one of the two datasets, and what they agree on is that addressing wrinkles alone leaves roughly half behind. This is developed in why the face still reads as the same age after the wrinkles are gone.
Classes that point the right way for settled lines
These target the density and texture of the dermis. But the thickness of the evidence differs greatly between them.
| Class | Best available human data | Can it be reversed? |
|---|---|---|
| Rejuran (polynucleotide) | Korean medical-device phase 3, 70 analysed (improvement 95.7% versus 94.3%) — but what it proved reaches only “not inferior to a hyaluronic acid product” | Degradable |
| Radiesse (CaHA) | Randomised, no-treatment control, 152 patients; improvement at 24 weeks 71.2% versus 6.3% | Not dissolved by hyaluronidase |
| Sculptra (PLLA) | Two randomised trials registered with the US FDA | Not dissolved by hyaluronidase |
| Ellanse (microsphere PCL) | Human biopsy in 13 patients (+26.7% ± 9.3% dermal thickness at one year) | Not dissolved by hyaluronidase |
| GOURI (liquid-form PCL) | 33 people in total, longest follow-up 6 months, no human biopsy | Not dissolved by hyaluronidase |
| Radiofrequency (RF) | A 2026 systematic review of 15 studies and 1,230 patients, of which one was a randomised controlled trial | Not applicable |
The classes as a whole are set out in what gets called a collagen booster.
On combining treatments — objectively
With fine lines, an expression cause and a dermal cause are often present together, which is how a plan addressing both directions arises. But “combining them works better” was not confirmed in the two randomised trials. Our reason for treating in parallel is not that it is more effective but that there are two causes. When there is one cause, we do one thing. We also say plainly that when several things are done together, it cannot be worked out afterwards which one acted.
The order we look in consultation
- We look at the relaxed photograph first. Whether the line persists with no expression is the first fork.
- We separate regions. Around the eyes, around the mouth and the forehead carry different proportions of muscle involvement.
- We assess the dermis. How far it has thinned changes the layer and the amount.
- We set the point of judgment in advance. It differs by class — radiofrequency was significant at 12 weeks with a peak at 4 to 6 months.
- We do not set the goal by wrinkles alone. With contributions splitting 37% wrinkles, 37% sagging and 26% pigmentation, addressing wrinkles alone leaves half behind.
Frequently asked questions
Is botulinum toxin right for fine lines?
If the lines appear only with expression, the direction is right. If they remain with no expression, muscle action is not the main cause and the result will fall short of the expectation.
Do boosters make fine lines go away?
“Soften” is the accurate word rather than “go away”. And the thickness of the evidence differs greatly between classes — Rejuran has a Korean phase 3 with 70 analysed, while GOURI has 33 people in total.
What about fine lines around the eyes?
The skin around the eyes is thin, so the layer and the amount must be judged particularly conservatively. Case reports describe nodules and irregularity more often in thin skin.
How much improves in one session?
It differs by class, and trials comparing results by session count are scarce. Self-assessment is also unstable — in one study, at 90 days 92% of operators saw improvement against 42% of patients. We work from photographs taken under the same conditions.
Which comes first, fine lines or firmness?
In Flament 2021 the contributions were effectively tied (wrinkles 37%, sagging 37%). Rather than asking which comes first, it is more useful to determine on examination which is larger in your own face.
Which clinic in Daegu is good for fine lines?
There is no public metric, so it cannot be answered from data. It is more useful to ask “are my fine lines from expression or from the dermis?” and choose the clinic whose answer is specific.
Who wrote this
Written and reviewed by Lee Chi-Hak, MD, medical director of Miso Clinic in Daegu, South Korea. Every study cited above is given together with its design, its size and the limitations the authors themselves recorded, and where we could not find data, we have said that we could not find any.
| Medical director | Lee Chi-Hak, MD |
|---|---|
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References
- Flament 2021 — 112 Korean women rated by 92 assessors; contribution to perceived age: wrinkles 37%, sagging 37%, pigmentation 26%
- Fink & Matts 2008 — removing facial surface topography, −10.84 years; removing colour alone, −1.05 years
- J Korean Med Sci 2014;29(Suppl 3):S201–S209 — Rejuran (PN) phase 3, 70 analysed
- Fabi S et al., Aesthet Surg J 2026, PMID 42424535, NCT05163353 — CaHA with no-treatment control, 152 patients, 71.2% versus 6.3% at 24 weeks
- 2026 systematic review — radiofrequency, 15 studies and 1,230 patients, one randomised controlled trial
- Point of judgment — at 90 days, operators 92% versus patients 42%; radiofrequency significant at 12 weeks, peak at 4 to 6 months
Everything in this column is general information and does not replace medical diagnosis or treatment. Effects and side effects vary with individual skin condition, age and underlying illness, and the same result is not guaranteed for everyone. Any decision to proceed should be made in an in-person consultation with a physician.
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