Seoul
Chief MD, Gangnam
Duk-ha Kim
The trust our patients have placed in this clinic was built on conviction and principle. We intend to hold to both, unchanged, through the next hundred years.
Acne scar guide by scar type and evidence certainty
Acne Scar Treatment
Acne scarring is a separate question from active acne, and the evidence behind treating it comes from several different kinds of sources that do not carry equal weight. A Cochrane review of 24 randomised trials found only one comparison, filler against placebo, reaching moderate certainty; a larger 2024 network meta-analysis ranks combinations by a statistical score without establishing which option best avoids pigmentation risk; and a 2024 expert consensus maps specific approaches to icepick, boxcar and rolling scars without assigning any of them a quantitative evidence grade.
- Cochrane review scale
- 24 randomised trials, 789 adult participants
- Highest-certainty finding
- Filler vs placebo, moderate certainty, measured at 24 weeks
- Network meta-analysis scale
- 68 randomised trials, 4,480 participants, search to September 2024
- Scar-type treatment map
- Expert consensus (Cureus 2024) — not a graded meta-analysis
What counts as an acne scar, and how are the main types classified?
Once active inflammation has settled, what remains for some people is a structural change in the skin rather than the breakout itself. A 2024 expert consensus on acne scar management groups these into three shapes — icepick, boxcar and rolling — and uses that same classification to map treatment choice by type, which several sections below build on. This page covers that residual scarring specifically, a separate question from treating an active breakout.
Sources: Cureus 2024 — expert consensus on acne scar treatment by scar type
How large is the Cochrane review behind acne scar treatment comparisons?
The Cochrane review carries the weight of 24 randomised trials and 789 adult participants, evaluating interventions for acne scars against each other and against placebo or no treatment. Trials in the review followed participants for up to 48 weeks, which sets the outer edge of what the pooled evidence can actually speak to — outcomes beyond that window are outside what these trials measured. Its scope covers commonly used approaches: dermal filler, fractional laser, radiofrequency, chemical peels and microneedling.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)
Which comparison did the Cochrane review rate with its highest certainty?
Filler compared with placebo was the one comparison the review rated at "moderate" certainty, with filler showing an advantage measured at 24 weeks. That is the single highest-certainty result in the entire review — every other comparison it made, including comparisons between different procedures rather than against placebo, sat at a lower certainty grade. A moderate rating means the true effect is likely close to what the trials found, but it is not the same as "proven" in an absolute sense, and it does not extend past the 24-week measurement point the trials used.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)
How do fractional laser, radiofrequency, chemical peels and microneedling compare with each other?
The review found these four approaches produced broadly similar results when compared against each other, but rated the certainty of that finding "very low" to "low" rather than moderate. Low certainty here means the true effect could differ substantially from what the pooled trials showed — the finding of similarity is itself uncertain, not a confirmed tie. None of these four comparisons reached the certainty level given to filler against placebo.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)
Does the Cochrane review recommend any single procedure as first-line treatment?
No. The stated conclusion of the review is that no procedure carries sufficient evidence to be recommended as a first-choice treatment for acne scars. That conclusion covers every approach it evaluated, including the filler-versus-placebo comparison that reached moderate certainty — a comparison being the most certain result in the review is not the same as the review endorsing that option as the recommended first step.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)
What does "evidence certainty" mean when a review rates something "very low" or "low"?
It is a statement about how much confidence to place in a finding, not a statement about whether a treatment works or fails. A "very low" or "low" certainty rating, the language the Cochrane review used for most of its comparisons, means further research is likely — or very likely — to change the estimate, often because trials were small, few in number, or produced inconsistent results across studies. Reading a low-certainty rating as "does not work" goes beyond what the rating actually says.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)
How large is the newer network meta-analysis of acne scar treatments?
A 2024 network meta-analysis behind more recent treatment comparisons pooled 68 randomised trials and 4,480 participants, with its literature search extending to September 2024. That scale lets it compare many treatment combinations against each other at once, rather than the pairwise structure of the earlier Cochrane review, though a network meta-analysis is a statistical way of ranking indirect comparisons rather than a substitute for head-to-head trial evidence for any single pair.
Which combination ranked highest for scar-assessment improvement in that analysis?
Laser combined with platelet-rich plasma (PRP) ranked highest, with a SUCRA score of 98.4% for improving scar-assessment scale scores. SUCRA is a ranking statistic that summarises where a treatment tends to fall across the network of comparisons — a higher score means the treatment more consistently ranked well against the others included, based on the scale the trials used to grade scar appearance.
Does a top SUCRA ranking mean that combination is proven the right choice for everyone?
No — a SUCRA ranking summarises probability across indirect comparisons, and the authors themselves listed specific limits on what this analysis established. They did not perform a subgroup analysis by Fitzpatrick skin type, and the trials feeding the network were concentrated in a small number of countries, so the ranking describes how treatments performed across the pooled trial population rather than a personal prediction for any one reader.
Does the network meta-analysis identify a treatment that reliably lowers redness or dark-mark risk?
No. The authors wrote that no treatment showed significant evidence for lowering the risk of erythema or post-inflammatory hyperpigmentation. That is a direct limitation stated in the analysis itself: the SUCRA ranking above concerns improvement on a scar-assessment scale, and it does not carry over to a separate finding about which option best avoids redness or dark marks as a side effect.
Where were the trials in that meta-analysis conducted, and why does that matter?
The included trials concentrated in a small number of countries — 21 from India, 18 from Egypt and 12 from China among the total, with the remainder spread more thinly elsewhere. That concentration matters because the analysis did not stratify results by Fitzpatrick skin type, so a reader cannot use the country count as a stand-in for how the findings apply to any particular skin tone; it is a note about where the pooled evidence comes from, not a finding about skin type at all.
How does the expert consensus map treatment choice to each scar type?
The 2024 consensus statement lines up a specific approach against each scar shape: icepick scars toward TCA CROSS or punch excision, shallow boxcar scars toward resurfacing, deeper boxcar scars toward subcision combined with punch elevation, and rolling scars toward subcision combined with dermabrasion. The comparison table below sets these out side by side, and identifying which shape, or combination of shapes, is actually present is a starting question for that mapping to apply at all.
Sources: Cureus 2024 — expert consensus on acne scar treatment by scar type
Is that scar-type map based on the same kind of evidence as the two reviews above?
No, and the distinction matters. The scar-type map comes from an expert consensus statement, not from a meta-analysis, and it does not assign a quantitative certainty grade to any of its recommendations the way the Cochrane review or the network meta-analysis do. That does not make the mapping arbitrary — consensus statements reflect experienced clinical judgment brought together deliberately — but it is a different evidence category from a pooled trial comparison, and treating it as if it carried the same certainty rating would overstate what it is.
Sources: Cureus 2024 — expert consensus on acne scar treatment by scar type
What does the expert consensus suggest for lowering pigmentation risk in darker skin tones?
For Fitzpatrick IV to VI skin, the consensus statement points to two adjustments: lowering the treatment density and the number of passes during a procedure, and using a lightening agent before and after the session. Those are the specific levers the statement names — it does not claim these adjustments eliminate pigmentation risk, and it stops short of naming any single procedure as the safest option for darker skin.
Sources: Cureus 2024 — expert consensus on acne scar treatment by scar type
Is there controlled-trial evidence for reducing pigmentation risk after a specific laser procedure?
One randomised trial addresses this directly for fractional CO2 laser. It enrolled 29 participants with Fitzpatrick skin types III to V and compared adding a peeling step before and after the laser session against the laser alone; the group that received the peeling step had a significantly lower pigmentation index at six weeks (p=0.015). The trial was run at a single center with a small sample, which limits how far the result can be generalised, but it is the one piece of controlled-trial evidence on this page addressing pigmentation risk after a named procedure rather than describing it in general terms.
What can these studies not tell you about your own risk of pigmentation after treatment?
Each source on this page has a specific limit that keeps it from generalising to an individual case. The network meta-analysis did not run a subgroup analysis by Fitzpatrick skin type despite drawing many of its trials from countries where medium-to-dark skin tones are common. The consensus mapping is expert opinion without a quantitative grade. And the peeling trial for post-laser pigmentation enrolled only 29 people at a single center. None of that removes the value of the sources — it means an in-person assessment of your own skin type, scar type and history is the step none of them can substitute for.
Sources: Network meta-analysis of acne scar treatments (68 randomised trials, 4,480 participants, search to September 2024)Cureus 2024 — expert consensus on acne scar treatment by scar typeJ Cosmet Dermatol 2025 — randomised trial of a peeling adjunct for post-inflammatory hyperpigmentation after fractional CO2 laser (n=29, Fitzpatrick III-V)
How long does an improvement in acne scarring last once treatment stops?
None of the sources behind this page followed scarring outcomes past the point their trials were designed to measure, so any duration named here is the length of a measurement window, not a promise about your skin afterward. The Cochrane review’s highest-certainty finding — filler outperforming placebo — was measured at 24 weeks, and the trials in that review followed participants for up to 48 weeks at the outside; nothing in the review reports what the scar-assessment score does in year two or beyond, because the trials were not run that long. The peeling-adjunct trial for pigmentation after fractional CO2 laser measured its result at six weeks, a shorter window than either Cochrane figure. The network meta-analysis of 68 trials adds a ranking rather than a timeline: a SUCRA score describes how consistently laser combined with PRP outranked other options across the pooled comparisons, and that statistic says nothing about how long any one person’s improvement holds, because ranking and duration are different questions the same data cannot both answer. What actually determines how a scar looks a year after a course of treatment is outside all of these figures — it depends on which scar type is present, as mapped in the expert consensus above, how many sessions were completed, individual healing response, and whether new acne activity adds fresh scarring during or after the course. The consultation question that follows directly is what outcome window the clinic is quoting when it describes a result, and whether that window matches the 24-week, 48-week or six-week points these trials actually used rather than an unstated longer claim.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)Network meta-analysis of acne scar treatments (68 randomised trials, 4,480 participants, search to September 2024)J Cosmet Dermatol 2025 — randomised trial of a peeling adjunct for post-inflammatory hyperpigmentation after fractional CO2 laser (n=29, Fitzpatrick III-V)Cureus 2024 — expert consensus on acne scar treatment by scar type
What should you confirm with the clinic before choosing a scar procedure?
Start with which scar type or combination of types is present, since the consensus mapping above only applies once that is identified. Ask where the proposed approach sits in the evidence — whether it is the filler-versus-placebo comparison rated moderate certainty, one of the lower-certainty procedure comparisons, a position from the network meta-analysis, or a consensus recommendation without a quantitative grade. If you have a darker skin tone, ask specifically whether treatment density, pass count, and a pre- and post-procedure lightening step are being adjusted, and what evidence that adjustment is based on. And ask what outcome window the clinic is using to judge results, since the trials referenced here measured effects at 24, 48 and 6 weeks, not indefinitely.
Sources: Cochrane review CD011946 — interventions for acne scars (24 randomised trials, 789 participants)Network meta-analysis of acne scar treatments (68 randomised trials, 4,480 participants, search to September 2024)Cureus 2024 — expert consensus on acne scar treatment by scar typeJ Cosmet Dermatol 2025 — randomised trial of a peeling adjunct for post-inflammatory hyperpigmentation after fractional CO2 laser (n=29, Fitzpatrick III-V)
Which approach does the expert consensus map to each acne scar type?
This table sets out the scar-type-to-approach mapping from the 2024 expert consensus statement, side by side. It is a consensus opinion, not a ranked comparison of effectiveness, and it does not carry the certainty grading used in the Cochrane review or the network meta-analysis above — identifying which scar type is actually present is a question for an in-person assessment, not this table.
| Scar type | Consensus-mapped approach | Evidence category | What to ask about pigmentation risk |
|---|---|---|---|
| Icepick | TCA CROSS or punch excision | Expert consensus, not a graded trial comparison | Ask about treatment density and any pre/post lightening step for darker skin tones |
| Boxcar (shallow) | Resurfacing | Expert consensus, not a graded trial comparison | Ask the same density and lightening-step questions before a resurfacing session |
| Boxcar (deep) | Subcision combined with punch elevation | Expert consensus, not a graded trial comparison | Ask how the plan accounts for pigmentation risk given the additional subcision step |
| Rolling | Subcision combined with dermabrasion | Expert consensus, not a graded trial comparison | Ask whether pass count and density are adjusted for your skin tone before dermabrasion |
This mapping is expert opinion, not a graded meta-analysis, and none of the sources on this page rank one scar-type approach as superior to another in effectiveness. Confirming which scar type is actually present, and discussing pigmentation-risk adjustments for your skin tone, are in-person questions this table does not answer on its own.
Sources: Cureus 2024 — expert consensus on acne scar treatment by scar type
Medical care at Abijou
Care is provided by the medical team at the branch you select. These clinicians lead the three branches linked from this guide; confirm the doctor assigned to your visit with that branch.
Chief MD, Myeongdong
Cheol-su Yoon
I want to be thinking about how the patient feels right up to the last moment of the procedure.
Chief MD, Hongdae
Jae-wook Kim
I will give my best with the attentiveness to catch even the smallest change.
Listed branch medical team — not a medical-review byline for this article.
Frequently asked questions
What counts as an acne scar, as distinct from a red or dark mark left after a breakout?
An acne scar in the sense used on this page is a structural change in the skin, grouped by a 2024 expert consensus into icepick, boxcar and rolling shapes, rather than the temporary redness or pigmentation that can follow a breakout. That distinction matters for reading the rest of this page correctly: the Cochrane review and network meta-analysis discussed below evaluate treatments for that structural scarring, while a separate randomised trial referenced further down looks specifically at pigmentation risk after one type of laser procedure, a different outcome being measured.
Which single comparison did the Cochrane review rate with its highest certainty?
Filler compared against placebo, measured at 24 weeks, is the one comparison the review rated "moderate" certainty — every other comparison in the review, including comparisons between different procedures, was rated lower. The review pooled 24 randomised trials and 789 adult participants across all of its comparisons, with follow-up extending up to 48 weeks in the included trials.
Does that mean filler is the recommended treatment for acne scars?
No — the review states directly that no procedure has sufficient evidence to be recommended as a first-line treatment, and that statement covers every option it evaluated, filler included. Being the comparison with the least uncertainty is not the same as being endorsed as the recommended choice; it describes how confident the review can be in that one result, not a verdict on which treatment to pick.
How reliable is the evidence comparing fractional laser, radiofrequency, chemical peels and microneedling against each other?
The review found these four approaches produced broadly similar results, but rated that finding "very low" to "low" certainty rather than moderate. A rating that low means further research could change the picture substantially, so the similarity itself should be read as an uncertain finding rather than a settled tie between these options.
What does a network meta-analysis add that the earlier Cochrane review does not?
A 2024 network meta-analysis pooled a larger and more recent body of evidence — 68 randomised trials and 4,480 participants, with its search extending to September 2024 — and used that scale to rank multiple treatment combinations against each other rather than working through comparisons pair by pair. It is still built from indirect statistical comparisons across trials rather than head-to-head evidence for every pair it ranks.
Which combination ranked highest in that analysis, and does the ranking mean it works best for everyone?
Laser combined with platelet-rich plasma (PRP) ranked highest, with a SUCRA score of 98.4% for improving scar-assessment scale scores, but the authors were explicit about what that ranking does not establish. They did not run a subgroup analysis by Fitzpatrick skin type, and the trials behind the ranking were concentrated in a small number of countries, so the score describes performance across the pooled population rather than a personal prediction for any individual reader.
Does the network meta-analysis show which treatment best avoids redness or dark marks as a side effect?
No — the authors stated directly that no treatment in the analysis showed significant evidence for lowering the risk of erythema or post-inflammatory hyperpigmentation. That statement sits alongside the SUCRA ranking for scar-assessment improvement, and the two should not be read together as if a high scar-improvement ranking also means a lower pigmentation-risk ranking; the analysis does not support that link.
Where were the trials in that meta-analysis conducted?
The largest concentrations came from India (21 trials), Egypt (18 trials) and China (12 trials), with the remaining trials spread more thinly across other countries. The analysis did not stratify its results by Fitzpatrick skin type, so this country breakdown describes where the evidence originated rather than telling you how the findings translate to a specific skin tone.
How does the expert consensus match a treatment approach to each scar type?
It matches icepick scars to TCA CROSS or punch excision, shallow boxcar scars to resurfacing, deeper boxcar scars to subcision combined with punch elevation, and rolling scars to subcision combined with dermabrasion. The comparison table on this page sets these four pairings out side by side, and identifying which scar type is actually present is the step that has to happen before this mapping can be applied.
Is that scar-type mapping backed by the same kind of evidence as the Cochrane review or the network meta-analysis?
No — it comes from an expert consensus statement rather than a meta-analysis, and it does not carry a quantitative certainty grade the way the two pooled-trial analyses above do. That is a difference in evidence category, not a reason to dismiss the mapping, but it should not be read as if it had passed through the same grading process as the Cochrane review or the network meta-analysis.
What does the expert consensus recommend for reducing pigmentation risk in darker skin tones (Fitzpatrick IV to VI)?
It points to two specific adjustments: lowering the treatment density and number of passes during a procedure, and using a lightening agent before and after the session. The consensus statement does not claim these steps remove pigmentation risk entirely, and it does not name any single procedure as the safest option for darker skin — it names adjustments to how a procedure is performed rather than which procedure to choose.
Is there a randomised trial testing a way to lower pigmentation risk after a specific procedure?
Yes — a randomised trial in 29 participants with Fitzpatrick skin types III to V compared adding a peeling step before and after fractional CO2 laser against the laser alone, and found a significantly lower pigmentation index at six weeks in the peeling group (p=0.015). The trial was conducted at a single center with a small sample, so the result should be read as an early finding rather than an established standard.
Can any of these studies tell me my own personal risk of pigmentation after a scar procedure?
Not directly — each study has a specific limitation that keeps it from generalising to an individual case. The network meta-analysis did not stratify by Fitzpatrick skin type, and the peeling trial enrolled only 29 participants at one center, so neither source can substitute for an in-person assessment of your skin type, scar type and treatment history.
What should you ask the clinic before choosing a scar procedure?
Ask which scar type or combination of types is present, since the consensus mapping and the comparison table on this page only apply once that is identified. Ask where the proposed approach sits in the evidence — a moderate-certainty comparison, a lower-certainty one, a network meta-analysis ranking, or an ungraded consensus recommendation — and, if you have a darker skin tone, ask specifically whether treatment density, pass count and a pre/post lightening step are being adjusted and on what basis.
How Abijou works
We started in Gangnam in 2006 and the network now runs 17 branches across Korea. The line we work to is skin transformation woven into everyday life — care you can keep up with, rather than one dramatic change.
- Across the 17 branches in Seoul, Gyeonggi, Incheon and Busan: over 1,000 medical professionals and more than 350 certified medical devices
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