CO₂ laser for acne scars: which type of scar responds and which needs something more

Acne scarring is the indication with the most literature behind the CO₂ laser, and even so the useful question is not “does the laser work?”, but “what kind of scar do I have?”. Because a face with past acne almost never has one single type of scar, and they do not all respond in the same way to the same thing: there are scars the laser improves well on its own and others in which, without a prior step, the laser achieves little however many sessions are done.

This page explains how those scars are classified, what the evidence supports about the fractional CO₂ laser, when it has to be combined with other techniques and what improvement it is reasonable to expect.

This page sets out one of the indications for the fractional CO₂ laser. If your question is which technology suits your problem, the comparison is in CO₂ laser or intense pulsed light.

The three acne scars, and why telling them apart changes the treatment

The classification that has been used for more than twenty years describes three types of atrophic scar, and it is deliberately simple so that it works in front of the patient:

• Icepick. Narrow and deep, as though a punch had gone in vertically. It occupies little surface but reaches a long way down.
• Boxcar. With sharp edges and almost vertical walls, and a flat floor. Wider than the icepick and not as deep.
• Rolling. With soft, undulating edges and no defined wall. What produces it is not a loss of tissue at the surface, but a band tethering the skin to the deep plane; that is why it shows more in side lighting than head on.

The distinction is not academic. The laser works from the surface downwards: it vaporises microcolumns of tissue and prompts a repair that remodels the surrounding framework. That fits well with a scar whose problem lies at the surface and in the relief. It fits less well when the problem is a deep tether —the rolling scar— or a narrow channel the laser cannot reach to fill —the icepick.

What the evidence supports about the CO₂ laser

The reference systematic review searched five databases and the period from January 1987 to December 2016. From 337 initial articles it selected 30 studies: 12 retrospective and 18 randomised clinical trials. Its conclusion is that the ablative fractional CO₂ laser is an effective treatment for acne scarring.

And it then sets three conditions that are, in practice, as important as the conclusion:

1. The session, the interval between sessions and the settings must be individualised. There is no “acne scar programme” applied the same way to everybody.
2. In icepick scars, combined treatment should be considered. That is: the very review that supports the laser says that in that subtype the laser alone is not the plan.
3. Dermocosmetic care before and afterwards can benefit the patient.

A second systematic review, focused specifically on energy-based techniques, puts the result in context: ablative lasers appear to achieve the greatest degree of efficacy, but with significant recovery and a pigmentary risk, whereas non-ablative fractional photothermolysis has a far safer profile and does not reach the same aesthetic results. Those same authors point out a general lack of high-quality evidence across the whole field and call for standardised assessment scales.

It is an honest conclusion and worth passing on as it stands: there is support for treating, there is none for promising a specific figure for improvement.

When the laser does not go alone

Here is the difference between a planned treatment and a session that has been sold. The techniques combined with the laser are not a commercial extra: each one resolves a problem the laser does not.

• Subcision. A needle is used to release the band tethering the rolling scar to the deep plane. The systematic review of non-energy-based techniques records improvements of 10% to 100% depending on the study, a very wide range that reflects how heterogeneous the literature is, not a promise.
• TCA CROSS. Application of high-concentration trichloroacetic acid inside the channel of the icepick scar itself. In that same review, more than 70% improvement in 73.3% of patients, with better results than glycolic acid.
• Punch excision or elevation. For a deep boxcar scar with very sharp edges, removing or raising the floor can be more effective than trying to bring it down with energy.
• Microneedling. In the same review, all the patients treated improved to some degree, in a range of 31% to 62%. It is an option with less recovery and a lower ceiling, useful when skin type or the moment in life makes the ablative approach unwise. It is described in microneedling.

Put another way: the order matters. In a face with mostly rolling scars, releasing first and treating afterwards usually achieves more than starting by turning the laser energy up.

The acne has to be under control first

Treating scars on a skin that is still breaking out is starting the house from the roof: new scars will appear and the active inflammation increases the risk of the laser’s own insult leaving a mark.

On isotretinoin the full picture is worth giving, because for decades a rule was repeated —waiting between six and twelve months before any procedure— that the later evidence has not supported.

A systematic review with a multidisciplinary consensus published in 2017, which analysed 32 publications and 1,485 procedures, assessed exactly that question. Its conclusions:

• There is not enough evidence to delay fractional lasers, ablative and non-ablative, or laser hair removal, or superficial peels, or skin surgery, or manual dermabrasion, in patients who are taking isotretinoin or have recently taken it.
• What is advised against, with systemic isotretinoin, is mechanical dermabrasion and fully ablative laser.

Applied to what is done here, the distinction is clean and worth knowing: at ICPM the CO₂ laser is always used in fractional format, both in the gentle treatments and in the high-density, high-power ones. Full-field work is not done. That places both formats in the consensus’s first group —the one for which there is not enough evidence to justify postponement— and leaves the warning about fully ablative laser outside what is offered at the centre.

The authors add a consequence that matters to anyone in this situation: being able to have that evidence-based conversation means that, for some patients, treatment can be done sooner and be more effective, rather than waiting because of a rule with no backing. Even so, it remains a decision taken case by case in consultation, weighing the state of the skin and the aim of the treatment.

Skin type, sun and the risk of pigmentation

The risk that most determines the indication in a Mediterranean skin is not the scar: it is the pigment. The review of complications of fractional resurfacing points out that the likelihood of a complication is greater in sensitive areas of skin, in patients with intrinsically darker skin types and in those with predisposing medical risk factors. In a series of 961 treatments with a non-ablative fractional laser, post-inflammatory hyperpigmentation was the effect that appeared most often in the darker skin types, while the rest of the complications were spread evenly.

Translated into the consulting room: tanned skin or sun exposure expected in the near future postpone the treatment, and sun protection afterwards is not cosmetic advice but part of the treatment. It is set out in full in the risks of the CO₂ laser and in recovery day by day.

How many sessions and what improvement it is reasonable to expect

There is no figure that can honestly be given in advance. The reference systematic review concludes precisely that: sessions, intervals and settings are individualised.

What can be said is how it is planned:

• The starting point is which types of scar predominate on that particular face, not a fixed number of sessions.
• A plan is agreed that may include a prior step —subcision, CROSS, punch— before the first laser session.
• The response is reviewed and it is decided whether to carry on, space out or stop. The collagen goes on remodelling for months: the result is not judged at four weeks.
• The realistic aim is to improve the relief and the way light falls on the skin, not to leave the skin as though there had never been any acne.

A centre that offers a fixed number of sessions and a percentage of improvement before looking at your face is working to a commercial criterion.

When we do not offer it

• Uncontrolled active acne.
• Tanned skin, recent sun exposure or exposure expected in the near future.
• Active infection in the area, including a herpes outbreak.
• A history of keloid or hypertrophic scarring, which calls for a specific assessment.
• Being unable to take on the recovery time at this point in your life.
• An expectation that the laser will eliminate the scars rather than improve them.

A high skin type is not an absolute contraindication, but it changes the settings, the preparation and the conversation about risks.

Frequently asked questions

Does the CO₂ laser eliminate acne scars?

No. It improves them. The evidence supports the ablative fractional CO₂ laser as effective on atrophic acne scarring, and none of the available reviews supports complete disappearance.

How many sessions will I need?

It depends on the type of scar that predominates, on your skin type and on the response. The reference systematic review concludes expressly that the session, the interval and the settings must be individualised, so giving a number before examining the skin would be inventing one.

I have very narrow, deep scars — is the laser any use to me?

Those are the icepick type, and there the very review that supports the laser recommends considering combined treatment. It usually makes more sense to treat the channel —with TCA CROSS or with excision, for instance— and use the laser for the whole.

Is the laser or microneedling better?

It is not a race between two techniques. Ablative lasers achieve greater efficacy and also more recovery and more pigmentary risk; microneedling has a lower ceiling and a gentler profile. Which suits you depends on the type of scar, on your skin type and on how many days you can stop.

Can I be treated if I am taking isotretinoin?

A multidisciplinary consensus from 2017, on 32 publications and 1,485 procedures, found no sufficient evidence to delay fractional lasers in patients taking isotretinoin or who have recently taken it. That same consensus does advise against fully ablative laser while on the drug, but at ICPM the CO₂ is always used in fractional format, so that warning does not affect the treatments offered here. Even so, it is a conversation had in consultation, case by case.

Can it be done in summer?

It is the worst time of year. Tanned skin and expected sun exposure increase the risk of pigmentation, and strict sun protection for months is part of the treatment, not an add-on.

Is it going to hurt?

Topical anaesthetic is applied and, depending on the intensity and the area, local infiltration may be added. The sensation during the shot is one of heat and stinging.

What if I have darker skin?

It is not an absolute contraindication, but it is the factor that most changes the plan: the settings come down, the preparation is stepped up and the risk of post-inflammatory hyperpigmentation is explained before starting.

Sources

• Xu Y, Deng Y. Ablative Fractional CO2 Laser for Facial Atrophic Acne Scars. Facial Plast Surg. 2018;34(2):205-219. Systematic review of 30 studies (January 1987 – December 2016): 12 retrospective and 18 randomised trials. https://pubmed.ncbi.nlm.nih.gov/29304516/
• Jacob CI, Dover JS, Kaminer MS. Acne scarring: a classification system and review of treatment options. J Am Acad Dermatol. 2001;45(1):109-117. Classification into icepick, rolling and boxcar. https://pubmed.ncbi.nlm.nih.gov/11423843/
• Kravvas G, Al-Niaimi F. A systematic review of treatments for acne scarring. Part 1: Non-energy-based techniques. Scars Burn Heal. 2017;3:2059513117695312. Subcision, microneedling and TCA CROSS. https://pubmed.ncbi.nlm.nih.gov/29799567/
• Kravvas G, Al-Niaimi F. A systematic review of treatments for acne scarring. Part 2: Energy-based techniques. Scars Burn Heal. 2018;4:2059513118793420. https://pubmed.ncbi.nlm.nih.gov/30627441/
• Graber EM, Tanzi EL, Alster TS. Side effects and complications of fractional laser photothermolysis: experience with 961 treatments. Dermatol Surg. 2008;34(3):301-305. https://pubmed.ncbi.nlm.nih.gov/18190541/
• Metelitsa AI, Alster TS. Fractionated laser skin resurfacing treatment complications: a review. Dermatol Surg. 2010;36(3):299-306. https://pubmed.ncbi.nlm.nih.gov/20100273/
• Spring LK, Krakowski AC, Alam M, et al. Isotretinoin and Timing of Procedural Interventions: A Systematic Review With Consensus Recommendations. JAMA Dermatol. 2017;153(8):802-809. https://pubmed.ncbi.nlm.nih.gov/28658462/

Book your consultation

If you are carrying acne scars and do not know which ones you have, what settles the question is an assessment in person: the skin is examined under side lighting, the predominant type is identified and it is decided whether the laser goes alone or with company, and in what order.

Clinical confirmation by the surgeon

Dr Enrique Salmerón González

Specialist in Plastic, Aesthetic and Reconstructive Surgery
Registration no. 46/4624077

Dr Elena García Vilariño

Specialist in Plastic, Aesthetic and Reconstructive Surgery
Registration no. 46/4624503

Last reviewed: 23 August 2026. This content is for information only and does not replace an individual assessment by a healthcare professional.