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Technology · Target: water

How does a CO₂ laser work in the skin?

A CO₂ laser is absorbed by water. Light at 10,600 nm is taken up in the top few hundredths of a millimetre of the skin. There the tissue vaporises, and around it a rim of heat remains that coagulates the surrounding tissue. That heat is what gives CO₂ its particular character: there is little bleeding and collagen contracts. The laser is usually used in fractional mode, in a grid of narrow columns. Our device is the eCO2 3D.

Clinically reviewed by Marit van Boldrik, Business & Clinicallast checked 19 October 2026

Translated from Dutch with the help of AI tools; the clinical review was carried out on the Dutch text.

Water strongly absorbs 10,600 nm

The skin consists largely of water, and water strongly absorbs light at 10,600 nm [1]. After about 12 micrometres of water, only just over a third of that light remains. At 2940 nm, the Er:YAG wavelength, the same happens in less than 1 micrometre. Water therefore absorbs CO₂ light roughly fifteen times less strongly than erbium light [2].

Erbium light therefore stays closer to the surface, and reaching the same depth with erbium as with a single CO₂ pass takes more passes [3]. With CO₂, more heat remains around the vaporised zone. A comparison on the eyelids of nine patients shows this. After CO₂, the collagen contracted immediately because of the heat. Erbium produced comparable vertical tightening, but only after a month: the wound contracted as it healed [4]. What that difference means when choosing between the two is covered on the erbium page.

Absorption by water between 2000 and 12,000 nm, on a logarithmic scale. The curve peaks around 2940 nm, the Er:YAG wavelength (DualMode). At 10,600 nm, the CO₂ wavelength (eCO2 3D), it is about fifteen times lower. On the right is how far the light travels in water before it is attenuated to just over a third: about 0.8 micrometres at 2940 nm and about 12 micrometres at 10,600 nm.
Water absorbs light at 10,600 nm about fifteen times less strongly than light at 2940 nm. CO₂ light therefore reaches deeper, although still only micrometres, and heats a thicker layer around the vaporised zone.

Vaporisation and coagulation

If a pulse is short and powerful enough, the water in that thin layer boils off and the tissue vaporises with it. The heat that remains beneath and beside it coagulates the tissue. Every CO₂ zone therefore has two parts: a vaporised core and a rim of coagulated tissue.

How wide that rim becomes depends strongly on the pulse duration. In guinea pigs, pulses of 50 milliseconds, as delivered by a shuttered continuous-wave laser, produced a zone of thermal damage about 750 micrometres wide. With pulses of 2 microseconds, that zone could shrink to 50 micrometres [5]. Pulsed CO₂ lasers deliver short pulses of less than a millisecond and char the tissue less than a continuous beam [3].

That coagulated rim has two consequences that are typical of CO₂. The heat seals small blood vessels, so the treatment causes little bleeding [1]. And dermal collagen contracts when heated. With fully ablative CO₂ around the eyes and mouth, researchers unexpectedly saw that lax skin and folds also tightened. They attributed this to collagen contracting under the heat [6].

Full surface or fractional

Where the laser places those zones determines the balance between effect and recovery. In classic, fully ablative resurfacing, the laser vaporises the entire epidermis and part of the dermis across the whole treated area. Wrinkles and photoageing improve markedly as a result [6], but recovery takes a long time. In 500 patients, the skin stayed red for an average of 4.5 months. Hyperpigmentation occurred in 37%, more often in darker skin [7]. Hypopigmentation can also occur, often only after months [8]. In a series of 447 patients followed for a median of just over two years, it affected 6 to 9% [9].

With fractional CO₂, the laser vaporises only narrow columns, with intact skin in between. The first study in living human skin showed a sheath of coagulation around each vaporised column. With more energy per pulse, the columns became deeper and wider, and three months later the collagen was still remodelling [10]. The columns can reach deep into the dermis. In a study of periorbital syringomas, at the high energy used there, they reached just over 1.2 millimetres on average [11]. The epidermis re-epithelialises quickly from the intact skin in between [3]. A fractional treatment therefore needs less downtime and causes fewer complications than a fully ablative one, although more sessions are needed [12][13]. Serious complications have also been described after fractional treatments, more often in sensitive areas and in dark skin [13].

Two cross-sections of the skin. Left, fully ablative: the epidermis and upper dermis have been removed across the whole treated area, with a coagulated layer beneath and a narrower zone of heating. Right, fractional ablative: five narrow vaporised columns reach into the dermis, each with a rim of coagulation and a zone of heating, with intact skin in between. A legend shows heating at around 42–50 °C, coagulation above 60 °C and vaporisation from 100 °C.
Fully ablative treatment vaporises the epidermis across the whole area; fractional treatment vaporises narrow columns and leaves intact skin in between. Schematic, not to scale.

How the eCO2 3D places the zones

In a fractional treatment, how the laser distributes the columns over the skin also matters: how large they are, how deep they go and in what order they land. Our CO₂ device is the eCO2 3D from Cynosure Lutronic. The device has tips for microbeams of 120, 300 and 500 micrometres. The manufacturer distinguishes a static mode, for targeted and deeper treatments, and a dynamic mode, for treating the whole face faster and more lightly.

According to the manufacturer, the eCO2 3D places the microbeams in random order across the scan field. For the eCO2 range, Cynosure Lutronic describes the principle as follows: each microbeam lands as far as possible from the previous one, so that neighbouring zones are not heated in quick succession. The manufacturer calls this scan pattern Controlled Chaos Technology. It is the name of a scan sequence, not a type of laser: the same name also appears on the Mosaic 3D, a non-ablative laser at 1550 nm. We are not aware of any clinical studies measuring the effect of that sequence.

Two grids of 6 by 6 zones, the first 14 of which are numbered and coloured. On the left, the zones are fired row by row, so the last four, which are still warm, lie next to each other. On the right, they are fired in a scattered order, so the last four lie far apart. In each grid, a blue line connects the last four pulses.
Row by row, each new zone lands next to the previous one; in a scattered sequence, it lands far from the previous one. Cynosure Lutronic calls that scan pattern Controlled Chaos Technology. Schematic; the device's actual sequence is not public.

What it is used for

  • (Acne) scars

    In atrophic scars, such as acne scars, the dermis has to remodel. Fractional CO₂ vaporises narrow columns into the dermis, with a rim of coagulation that triggers collagen repair. According to a systematic review of seven studies, acne scars improved by 30 to 70% in most patients [14]. A meta-analysis of eight randomised studies found more improvement with fractional CO₂ than with RF microneedling, but also more pain, more frequent post-inflammatory hyperpigmentation (PIH) and longer-lasting redness [15]. For traumatic scars, too, an expert consensus sees an important role for ablative fractional treatment [16].

  • Wrinkles

    CO₂ works on wrinkles in two ways: the laser vaporises the upper layers, and the heat makes collagen contract and then be renewed. In older studies, fully ablative CO₂ clearly improved wrinkles around the eyes and mouth [6], but the skin stayed red for months on average [7]. In fractional mode, the effect per session is smaller, and so is the downtime [12]. After three sessions of fractional CO₂, wrinkles were measurably smaller and less deep, most markedly on the cheeks and around the eyes [17]. Around the eyes, fractional CO₂ and fractional Er:YAG gave a comparable effect after one session [18].

  • Skin rejuvenation

    Skin rejuvenation addresses advanced photoageing, in which wrinkles, lax skin, rough texture and pigment occur together. Fractional CO₂ treats the epidermis and the dermis in the same session. In one study, 56 Asian patients received a single treatment. In the 30 who were followed up for five years, the photoageing score at five years was still better than before treatment [19]. An international consensus of 21 dermatologists and plastic surgeons regards fractional CO₂ as a standard treatment for skin rejuvenation [20].

  • Skin quality improvement

    Skin quality improvement addresses texture, pores, fine lines and uneven skin tone, with as little downtime as possible. Fractional CO₂ can also be used superficially, so that mainly the epidermis and upper dermis are treated. For such a superficial treatment with the eCO2 3D, Cynosure Lutronic cites redness lasting 6 to 48 hours. After three sessions of fractional CO₂, pigment on the cheeks and around the eyes was more evenly distributed, a prospective study measured [17]. In dark skin, post-inflammatory hyperpigmentation (PIH) remains a risk, including after fractional CO₂ [21].

  • Skin tightening

    CO₂ can tighten the skin somewhat: under heat, collagen in the dermis contracts and is then renewed. After fully ablative CO₂ on the eyelids of nine patients, the skin was tighter straight away, and six months later much of that remained [4]. In nine other patients, a single fractional CO₂ treatment also significantly improved skin laxity [21]. If the main concern is laxity without wounds, monopolar RF is a technology to consider alongside CO₂.

  • Benign skin lesions

    A CO₂ laser vaporises tissue with little bleeding, because the heat seals small vessels [1]. This makes it possible to remove raised benign lesions. Syringomas around the eyes improved after two fractional treatments in most of 35 patients [11]. A lesion can also be removed in its entirety with a non-fractionated CO₂ beam. In xanthelasma, all lesions in 23 patients disappeared this way after one treatment; after ten months they had returned in three patients, and there were temporary pigment changes [22]. Vaporised tissue can no longer be examined histologically. Laser ablation is therefore only an option when the diagnosis is certain.

Skin type and pigment risk

CO₂ light is absorbed by water, not melanin. Skin colour therefore does not determine where the light ends up. Even so, PIH is the main risk in dark skin. An ablative treatment causes inflammation, and dark skin is more likely to respond with pigmentation [3].

How often PIH occurs depends on the skin type and the treatment. Of nine Chinese patients with skin types III and IV, five had PIH one month after a single fractional CO₂ treatment, and one after six months [21]. Of thirteen Asian patients with skin type IV and acne scars, twelve developed mild PIH after at least one of the three sessions, which had resolved after five weeks on average [23]. A series of 38 patients with skin types I to IV recorded no PIH [24]. With skin types V and VI, extra caution is warranted.

A review of aesthetic treatments in dark skin recommends fewer passes or a lower density for fractional resurfacing, along with adequate cooling. The authors avoid pulse stacking and short intervals between sessions. What they write about density is based largely on research with a non-ablative laser [3]. In the international consensus on fractional CO₂, more than 90% of the experts adjust their settings for skin types III and IV [20]. After fully ablative CO₂, there is also the risk of long-term hypopigmentation [8][9]. Discuss the pigment risk with your patient beforehand; a test patch can help gauge how the skin responds.

Recovery and what can go wrong

After a fractional CO₂ treatment, redness, swelling and crusting are to be expected. After deeper resurfacing with the eCO2 3D, redness can last a week or longer, according to Cynosure Lutronic. In acne scars, a meta-analysis found that recovery after fractional CO₂ took almost four days longer on average than after fractional erbium lasers (Er:YAG and non-ablative Er:glass combined) [25]. Another meta-analysis found that redness lasted almost two days longer than after RF microneedling [15]. After fully ablative CO₂, the skin stays red for months [7].

In both meta-analyses, fractional CO₂ was more painful than fractional erbium lasers and RF microneedling [25][15]. In the consensus, almost all experts use a topical anaesthetic, and most also use nerve blocks [20].

After ablative resurfacing, acne flare-ups, milia and eczema also occur, and herpes simplex can be reactivated. Of the 500 patients treated with fully ablative CO₂, 7.4% developed a herpes infection, including patients with no history of it [7]. In the consensus on fractional CO₂, more than 90% of the experts give antibacterial and antiviral prophylaxis. An active infection on the face is a contraindication for 95% of the panel. For two thirds, the same applies to a burn, recent sun exposure, pregnancy and breastfeeding [20]. Scarring is rare but does occur, including after fractional treatments, and more often in sensitive areas [7][13].

The isotretinoin package leaflet advises postponing cosmetic procedures, including laser treatments, until six months after the end of treatment. According to a consensus of the American Society for Dermatologic Surgery, superficial peels and non-ablative lasers do not need to be postponed; ablative lasers are not covered by that statement [26].

What the research says

CO₂ has been used in dermatology for decades, first in fully ablative mode and, since about 2007, in fractional mode as well [1][10]. A systematic review and meta-analyses have been published on fractional CO₂ for acne scars [14][15][25]. They show a clear improvement, with more pain and downtime than lighter techniques.

For wrinkles and photoageing, the effect of a single fractional session is measurable but modest. In the randomised study around the eyes, wrinkle depth decreased by about 20% and the wrinkle score by about 10% [18]. After three sessions, another study measured cheek wrinkles that were less than half their original size and depth [17]. According to the authors of the randomised study, repeating sessions erodes part of what fractional treatment gains: the shorter downtime [18].

Little has been published on the eCO2 3D itself. The FDA cleared it in 2025 without a clinical study, because the device is equivalent to its predecessor, the eCO2 Plus [27]. A study on excised pig skin compared the device at 30 and 40 W. At 40 W, the columns were on average 11.8% deeper and 7.3% narrower, with less charring at the rim. Three of the seven authors work for Cynosure Lutronic. They expect a clinical benefit from this, including in dark skin, but this study did not investigate that [28].

CO₂ alongside other technologies

Erbium

In acne scars, more patients achieved a clear improvement with fractional CO₂ than with fractional erbium lasers, Er:YAG and non-ablative Er:glass combined, but with more pain and longer downtime. When the meta-analysis counted only the randomised studies, the difference was not significant [25]. For wrinkles, the outcomes vary by study and by design [29][18]. The comparison is covered in more detail on the erbium page, with our DualMode and UltraClear devices.

RF microneedling

RF microneedling also works fractionally, but the heat comes from current delivered into the dermis through needles; on Genius, those needles are insulated. In the meta-analysis of eight randomised studies in acne scars, fractional CO₂ worked slightly better. RF microneedling caused less pain, less PIH and shorter-lasting redness [15]. Our device is Genius.

Non-ablative: 1540–1550 nm and thulium

Non-ablative fractional lasers heat columns of tissue without opening the skin. Recovery is faster; the effect per session is usually smaller [12]. In our range, these are the Mosaic 3D and the 1550 nm module of the FlexSys, and for more superficial work the LaseMD Ultra thulium laser at 1927 nm.

Monopolar RF

If the main concern is lax skin, with little downtime and no wounds, monopolar RF can be an alternative; in our range, that is the XERF.

Our devices using this technology

Cynosure Lutronic eCO2 3D laser device with handpiece on an articulated arm and touchscreen control panel
Cynosure Lutronic

eCO2 3D

Skin quality improvementSkin rejuvenationSkin tightening+3

Advice

Is this technology right for your practice?

A single page cannot fully cover the choice between technologies. It depends on your patients and their skin types, the indications you want to treat, the recovery time your patients will accept and the equipment you already have. Our clinical and sales specialists have years of experience with that choice and are glad to help you make it.

Already working with one of our devices? You will find the treatment protocols and guidelines on the customer portal, and we go deeper into technique in the training after delivery and at our Academy events.

Schedule a conversationGo to the customer portal

This is an indicative overview to explain how technologies differ. Actual settings are governed by the treatment protocols and guidelines.

References

  1. Omi T, Numano K. The Role of the CO2 Laser and Fractional CO2 Laser in Dermatology. Laser Ther. 2014;23(1):49–60. doi:10.5978/islsm.14-re-01
  2. Hale GM, Querry MR. Optical Constants of Water in the 200-nm to 200-μm Wavelength Region. Appl Opt. 1973;12(3):555–563. doi:10.1364/ao.12.000555Diagram 1: D. J. Segelstein (1981), via S. Prahl, Oregon Medical Laser Center (https://omlc.org/spectra/water/).
  3. Harnchoowong S, Vachiramon V, Jurairattanaporn N. Cosmetic Considerations in Dark-Skinned Patients. Clin Cosmet Investig Dermatol. 2024;17:259–277. doi:10.2147/ccid.s450081
  4. Fitzpatrick RE, Rostan EF, Marchell N. Collagen tightening induced by carbon dioxide laser versus erbium:YAG laser. Lasers Surg Med. 2000;27(5):395–403. doi:10.1002/1096-9101(2000)27:5<395::aid-lsm1000>3.0.co;2-4
  5. Walsh JT, Flotte TJ, Anderson RR, Deutsch TF. Pulsed CO2 laser tissue ablation: Effect of tissue type and pulse duration on thermal damage. Lasers Surg Med. 1988;8(2):108–118. doi:10.1002/lsm.1900080204Animal study (guinea pig).
  6. Fitzpatrick RE, Goldman MP, Satur NM, Tope WD. Pulsed Carbon Dioxide Laser Resurfacing of Photoaged Facial Skin. Arch Dermatol. 1996;132(4):395–402. doi:10.1001/archderm.1996.03890280047007
  7. Nanni CA, Alster TS. Complications of Carbon Dioxide Laser Resurfacing. An Evaluation of 500 Patients. Dermatol Surg. 1998;24(3):315–320. doi:10.1111/j.1524-4725.1998.tb04161.x
  8. Bernstein LJ, Kauvar AN, Grossman MC, Geronemus RG. The Short- and Long-Term Side Effects of Carbon Dioxide Laser Resurfacing. Dermatol Surg. 1997;23(7):519–525. doi:10.1111/j.1524-4725.1997.tb00677.x
  9. Lewis KG, Nahm WK, Schmidt AN, Moy RL. Lack of difference in the rates of hypopigmentation with 90-microsecond pulsed and longer dwell time carbon-dioxide laser resurfacing. J Am Acad Dermatol. 2004;50(2):247–252. doi:10.1016/j.jaad.2003.07.008
  10. Hantash BM, Bedi VP, Kapadia B, Rahman Z, Jiang K, Tanner H, Chan KF, Zachary CB. In vivo histological evaluation of a novel ablative fractional resurfacing device. Lasers Surg Med. 2007;39(2):96–107. doi:10.1002/lsm.20468
  11. Cho SB, Kim HJ, Noh S, Lee SJ, Kim YK, Lee JH. Treatment of Syringoma Using an Ablative 10,600-nm Carbon Dioxide Fractional Laser: A Prospective Analysis of 35 Patients. Dermatol Surg. 2011;37(4):433–438. doi:10.1111/j.1524-4725.2011.01915.x
  12. Preissig J, Hamilton K, Markus R. Current Laser Resurfacing Technologies: A Review that Delves Beneath the Surface. Semin Plast Surg. 2012;26(3):109–116. doi:10.1055/s-0032-1329413
  13. Metelitsa AI, Alster TS. Fractionated Laser Skin Resurfacing Treatment Complications: A Review. Dermatol Surg. 2010;36(3):299–306. doi:10.1111/j.1524-4725.2009.01434.x
  14. Ptaszek B, Czernecka M, Podsiadło S. The Use of a Fractional Laser in Acne Scar Treatment—A Systematic Review. Life (Basel). 2025;15(6):915. doi:10.3390/life15060915
  15. Argobi Y, Tobeigei F, Alasiri FI. Fractional CO2 Laser Versus Micro Needling Radiofrequency for Post Acne Scarring: A Meta‐Analysis of RCTs. J Cosmet Dermatol. 2026;25(3):e70765. doi:10.1111/jocd.70765
  16. Anderson RR, Donelan MB, Hivnor C, Greeson E, Ross EV, Shumaker PR, Uebelhoer NS, Waibel JS. Laser Treatment of Traumatic Scars With an Emphasis on Ablative Fractional Laser Resurfacing. JAMA Dermatol. 2014;150(2):187–193. doi:10.1001/jamadermatol.2013.7761Consensus of eight experts, based largely on clinical experience.
  17. Kohl E, Meierhöfer J, Koller M, Zeman F, Klein A, Hohenleutner U, Landthaler M, Hohenleutner S. Fractional carbon dioxide laser resurfacing of rhytides and photoageing: a prospective study using profilometric analysis. Br J Dermatol. 2014;170(4):858–865. doi:10.1111/bjd.12807
  18. Karsai S, Czarnecka A, Jünger M, Raulin C. Ablative fractional lasers (CO2 and Er:YAG): A randomized controlled double‐blind split‐face trial of the treatment of peri‐orbital rhytides. Lasers Surg Med. 2010;42(2):160–167. doi:10.1002/lsm.20879
  19. Tan J, Lei Y, Ouyang HW, Gold MH. The use of the fractional CO2 laser resurfacing in the treatment of photoaging in Asians: Five years long‐term results. Lasers Surg Med. 2014;46(10):750–756. doi:10.1002/lsm.22304
  20. Levy T, Lerman I, Waibel J, Gauglitz GG, Clementoni MT, et al. Expert Consensus on Clinical Recommendations for Fractional Ablative CO2 Laser, in Facial Skin Rejuvenation Treatment. Lasers Surg Med. 2025;57(1):15–26. doi:10.1002/lsm.23850Consensus of 21 experts via questionnaires; according to the authors, focused on one specific device.
  21. Chan NP, Ho SG, Yeung CK, Shek SY, Chan HH. Fractional ablative carbon dioxide laser resurfacing for skin rejuvenation and acne scars in Asians. Lasers Surg Med. 2010;42(9):775–783. doi:10.1002/lsm.20974Nine patients, one treatment.
  22. Raulin C, Schoenermark MP, Werner S, Greve B. Xanthelasma palpebrarum: Treatment with the ultrapulsed CO2 laser. Lasers Surg Med. 1999;24(2):122–127. doi:10.1002/(sici)1096-9101(1999)24:2<122::aid-lsm7>3.0.co;2-6
  23. Manuskiatti W, Triwongwaranat D, Varothai S, Eimpunth S, Wanitphakdeedecha R. Efficacy and safety of a carbon-dioxide ablative fractional resurfacing device for treatment of atrophic acne scars in Asians. J Am Acad Dermatol. 2010;63(2):274–283. doi:10.1016/j.jaad.2009.08.051
  24. Oloruntoba AI, Rodrigues M. Safety and Tolerability of Fractional CO2 Lasers for Facial Rejuvenation Across Fitzpatrick Skin Phototypes I–IV: Retrospective Cohort Study. J Cosmet Dermatol. 2026;25(5):e70917. doi:10.1111/jocd.70917Retrospective, 38 patients, skin types I–IV only.
  25. Song X, Zhi BW. Comparative efficacy and safety of fractional carbon dioxide and erbium-based fractional lasers for atrophic acne scars: A systematic review and meta-analysis. Lasers Med Sci. 2026;41(1):222. doi:10.1007/s10103-026-05022-z
  26. Waldman A, Bolotin D, Arndt KA, Dover JS, Geronemus RG, et al. ASDS Guidelines Task Force: Consensus Recommendations Regarding the Safety of Lasers, Dermabrasion, Chemical Peels, Energy Devices, and Skin Surgery During and After Isotretinoin Use. Dermatol Surg. 2017;43(10):1249–1262. doi:10.1097/dss.0000000000001166Consensus (Delphi) of the ASDS; statement on non-ablative and superficial procedures.
  27. U.S. Food and Drug Administration. 510(k) premarket notification K244060: eCO2 3D (Lutronic Corporation). FDA, 31 juli 2025. https://www.accessdata.fda.gov/cdrh_docs/pdf24/K244060.pdfNo clinical study submitted; equivalence based on the eCO2 Plus (K100610).
  28. Ryu HG, Park J, Kim H, Kim W, Lee HR, Ko J, Cho SB. Comparative Morphometric and Histometric Evaluation of Power-Dependent Tissue Ablation Using Fractional Carbon Dioxide Laser. Clin Cosmet Investig Dermatol. 2025;18:1901–1907. doi:10.2147/ccid.s534637Ex vivo, pig skin. Three authors work for Cynosure Lutronic; the article does not mention a conflict of interest.
  29. Adrian RM. Pulsed carbon dioxide and erbium-YAG laser resurfacing: a comparative clinical and histologic study. J Cutan Laser Ther. 1999;1(1):29–35. doi:10.1080/14628839950517066Fully ablative, not fractional.
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