Route · Device-based

Fractional laser: on this layer, fractional CO2 has become the benchmark rather than the thing being tested

The randomised acne scar trials we read are mostly **'something new against fractional CO2'**, and they almost always end in 'no significant difference in scar score'. In a 2025 picosecond comparison, mean ECCA scores did not differ (P = 0.209), and the microneedle radiofrequency comparison was similar. But **pigment and erythema measures rose significantly on the CO2 side.**

Last checked Sep 17, 2026

Korean classification Being checkedThe regulatory class has not yet been confirmed against a primary document. It will be filled in once it is.

A fractional laser treats skin in microscopic columns rather than burning the whole surface. Intact skin between the columns is what makes recovery faster; in Korea it goes by names such as Fraxel, fractional CO2 and Mosaic.

There are two broad families.

Ablative: CO2 (10,600 nm), Er:YAG (2,940 nm). These vaporise tissue — stronger effect, longer recovery.
Non-ablative: 1,550 nm, 1,565 nm, fractionated picosecond and others. The surface stays; only heat is delivered.

This is not a topical cosmetic. It is a device procedure performed in a clinic, and this layer is kept separate from the ingredient layer.

We have not opened the Korean device approval record, so the classification here says 'being verified'.

What is established

Moderate evidence

Whatever you put against fractional CO2, it tied

The 2025 acne scar trials we read have nearly identical structure — fractional CO2 on one side of the face, something new on the other.

2025 picosecond comparison (prospective, randomised, split-face): a 1,064 nm non-ablative picosecond laser with holographic optics on one side, three sessions at two-month intervals, fractional CO2 on the other. Assessed three months after the final session.

No significant difference in mean ECCA scores between the two lasers after treatment (P = .209).
The physicians' improvement assessment, however, was greater for the fractional CO2.

2025 microneedle radiofrequency comparison (randomised split-face pilot, 30 people, one session each): both showed comparable efficacy relative to baseline (p < .05). That trial also appears on this site's microneedle radiofrequency page — the same trial read from each page's point of view.

More trials share the structure: multiple 1,565 nm Er:glass sessions against a single fractional CO2 session; adipose extracellular matrix / stromal vascular fraction gel injection against fractional CO2 over 24 weeks. We could not confirm their detailed figures from the abstracts, so they are listed as sources only.

How to read it: repeated 'no difference' can mean two things. Fractional CO2 may already be good enough to be hard to beat, or the acne scar scales may not be sensitive enough to detect a difference. These trials alone cannot separate the two.

Randomised controlled trial in people · sample size not reported · 24 weeks · Compared with another active ingredient · Funding not declared · Endpoint scores from blinded assessors PMID 38924534
Randomised controlled trial in people · 30 participants · 26 weeks · Compared with another active ingredient · Funding not declared · Endpoint scores from blinded assessors PMID 40568948

Moderate evidence

But pigment and erythema measures rose on the CO2 side

If efficacy is comparable, the remaining question is what it costs.

The 2025 microneedle radiofrequency trial measured exactly that. Both sides of 30 faces were photographed with VISIA at baseline and at 1, 2 and 6 months, with melanin and erythema indices recorded.

Pain was more obvious on the fractional CO2 side.
Red area value, melanin index and erythema index increased significantly on the CO2 side.

This is the structural price of the ablative approach. Vaporising the surface means longer recovery, and that recovery can end in pigmentation.

It matters especially in darker skin. Post-inflammatory hyperpigmentation is more likely the darker the skin, and that this trial was run in China makes the result more meaningful.

The limits still apply: a 30-person pilot with a single session per side.

Randomised controlled trial in people · 30 participants · 26 weeks · Compared with another active ingredient · Funding not declared · Endpoint instrument measurement PMID 40568948

Not established

We found no trial comparing fractional CO2 itself against no treatment

This is the strangest fact on the page.

In acne scar trials, fractional CO2 is almost always on the control side. A new device appears and is compared against fractional CO2; a new injectable appears and is compared against fractional CO2. It serves as the benchmark.

And yet we found no randomised trial comparing fractional CO2 itself against doing nothing.

This is the same structure this site has written on fifteen procedure pages, but here it goes one layer deeper: if the thing used as the benchmark has never itself been tested that way, what does tying with it tell you?

In fairness: this does not mean fractional CO2 does not work. It physically vaporises tissue and drives a repair response, so the mechanism is clear, and it has been used clinically for a long time. But 'long used' is not something this site accepts as evidence.

And as the IPL page shows, a trial with an untreated control is not impossible. It can be done when someone chooses to.

PubMed — 미국 국립의학도서관 문헌 데이터베이스

Known risks

Pain during treatment; more pronounced with fractional CO2 in the trial above.
Downtime. The ablative approach leaves redness and crusting for days to a week or two.
Post-inflammatory hyperpigmentation. Melanin and erythema measures rose significantly on the CO2 side above. More caution is warranted in darker skin.
Infection and reactivation of herpes simplex.
Rarely scarring, persistent erythema and hypopigmentation.
Sun management matters especially during the recovery period.
Any adverse reaction is something to have seen by the clinic that performed the procedure.

What is not established

Fractional CO2 itself has never been compared against an untreated control.
Whether ablative or non-ablative is better — comparative trials mostly end in 'no difference'.
Optimal settings (energy, density, number of sessions, interval) are not standardised.
Evidence for indications beyond acne scars (pores, wrinkles, striae) is not covered on this page.
We have not verified the Korean device approval class.

Whether to have it done is a decision to make with a doctor.

What this article relies on

PubMed — 미국 국립의학도서관 문헌 데이터베이스National Library of Medicine · Checked on 2026-09-16