CO2 laser gone wrong: signs, causes and what can help

What can go wrong after CO2 laser?

Most fractional CO2 laser treatments heal as planned, and the problems that do occur are usually temporary: redness that lasts longer than expected, darker patches, breakouts or a cold sore flare. Less often, the skin becomes infected, scars or develops lighter patches.

Fractional CO2 laser is an ablative treatment. It vaporises fine columns of skin and leaves untreated bridges between them, which speeds healing. Because it removes tissue and creates a wound, recovery matters as much as the treatment itself. Expected healing usually follows this pattern:

• Days 0 to 1: sunburn-like redness, pinpoint oozing and swelling.
• Days 2 to 4: swelling peaks, and the skin looks bronzed and sandpapery as fine crusts form.
• Days 5 to 7: crusts flake off, revealing pink new skin.
• Weeks 2 to 4: pinkness fades, and the skin stays sensitive to heat and new products.

Complications are often linked to settings that were too deep or dense for the skin type, treatment over a tan or active melasma, infection in the open stage, or aftercare problems such as picking, sun exposure or using the wrong products.

The sections below explain each problem, how to tell it from normal healing, and when to see a doctor. For how the treatment is done at SkinRev Lab, see the main CO2 laser (Tetra Pro S3) page, and for the expected recovery in detail, see CO2 laser downtime.

How common are CO2 laser complications?

Most complications after fractional CO2 laser are minor and resolve, but temporary darkening is common in Asian skin, so it is planned for rather than treated as a surprise.

• A large review of patients treated with fractional lasers measured complications in 4.2% overall and 6.4% of those treated with fractional CO2. The authors described them as generally minor, and all resolved; the commonest were acne breakouts, skin rashes and cold sore flares (Cohen and colleagues, 2017).
• A small study of Asian patients treated with fractional CO2 measured darkening in just over half at one month, falling to about one in nine at six months (Chan and colleagues, 2010). The study was small, but most of the early darkening had faded by six months.
• A review of fractional resurfacing in Asian patients named darkening and worsening of melasma as the main complications, and found that more sessions at lower density, spaced further apart, typically gave the lowest risk of darkening without reducing results (Wat and colleagues, 2017).
• A 2024 review noted that redness and swelling are the commonest complications, that serious and long-lasting ones do occur, and that operator training, correct settings and antisepsis matter (Beutler and colleagues, 2024).

The practical message is that most people heal without lasting problems, while skin type, settings and aftercare strongly affect the risk. Your doctor will advise how this applies to your skin and scars.

Redness that lasts longer than expected

Pinkness after fractional CO2 usually fades over two to four weeks; redness that is still strong after about a month, or that is getting stronger rather than fading, is prolonged redness and should be reviewed. It is one of the less common complications, and it usually settles with time and gentle care.

What can prolong redness:

• Deeper or denser settings, or several passes over the same area.
• Sensitive skin, rosacea or a tendency to flush.
• Heat, exercise, saunas, alcohol or spicy food in the first weeks.
• Restarting exfoliating acids, retinoids or new products too soon.
• A contact reaction to a cream or ointment, which tends to itch.
• Low-grade infection, which tends to hurt and crust.

What usually helps: a bland moisturiser and gentle cleanser, cool packs if the skin feels hot, avoiding heat and new products, and daily sunscreen once the skin has closed. If a product is causing a reaction, stopping it matters. A doctor may advise a prescription anti-inflammatory cream for a short time.

Why it is worth a review: redness that persists can be a sign that the skin is still inflamed, which increases the risk of darker patches and, in some cases, scarring. A doctor can check for infection, a contact reaction or early scar formation, and adjust care before these become harder to manage. If redness remains once healing is complete, treatments aimed at redness may be considered later.

Darker patches after CO2 laser (PIH)

Darker patches after CO2 laser are post-inflammatory hyperpigmentation (PIH), the main risk in Asian skin, and they usually fade over months with strict sun protection and medical care. They tend to appear a few weeks after treatment, often just as the pinkness is fading, as a brown or grey-brown haze over the treated area.

What raises the risk:

• Skin that darkens easily, or a history of PIH after acne or earlier procedures.
• Active melasma, which heat can worsen.
• Higher density or deeper settings than the skin type tolerates.
• Sun exposure in weeks 2 to 12, even brief daily exposure.
• Prolonged redness or infection during healing.

What usually helps:

• A broad-spectrum SPF 50 every morning, reapplied outdoors, with a hat and shade. This is the most important step in lowering the risk.
• Gentle skincare and no exfoliating actives until the doctor advises.
• Where your doctor advises, a prescription lightening cream started at the right point in healing.
• Delaying the next session until the patch has faded, then using more conservative settings.

PIH that has not faded after several weeks, or keeps darkening, should be reviewed so the plan can be adjusted early. For more on these marks, see post-inflammatory pigmentation.

Infection and cold sores after CO2 laser

Infection after CO2 laser is uncommon, but rising pain after day two, yellow crusts, pus or fever need same-day medical care. In the first days the skin is an open wound, so bacteria, viruses and occasionally yeast can take hold.

Signs of bacterial infection:

• Pain that increases after day two instead of easing.
• Honey-coloured or yellow crusts, pus or a bad smell.
• Redness and swelling that spread rather than settle.
• Fever or feeling unwell.

Cold sores: in people who get cold sores, the virus can reactivate, often as clusters of small, painful blisters or punched-out sores within the first week, sometimes away from the lips. A doctor may prescribe antiviral tablets around the treatment date if you have a history of cold sores, so mention this at consultation.

Yeast infection is rare and can show as itching, white patches or small pustules under thick ointment.

What to do now: do not pick or scrub crusts, keep the skin clean as instructed, and contact the provider who performed the treatment or a doctor promptly. Infection is treated with the right prescription medicine, and early treatment lowers the risk of darker patches and scarring. Do not use leftover creams or tablets.

Lowering the risk: treatment is postponed if there is active acne, infection, a cold sore or an open wound. Afterwards, use only the recommended ointment at first, keep hands and pets away from the face, use clean pillowcases, and avoid gyms, saunas and swimming until the skin has closed.

Scarring and lighter patches

Scarring after fractional CO2 laser is uncommon, and it is usually linked to treatment that was too deep or dense, infection, or picking; early signs are a patch that stays open or crusted longer than the rest, or skin that becomes firm, raised and red. These signs need a doctor's review promptly, because early care can change the outcome.

Where scarring is more likely:

• Thin-skinned areas such as the neck, jawline and around the eyes, which need gentler settings.
• Areas that became infected or were picked.
• People prone to keloids or thick raised scars.
• Skin with a history of poor wound healing.

What may help, where appropriate: close wound care, treatment of any infection, silicone gel or sheets, and, for raised scars, anti-inflammatory creams or injections or laser treatment once healing allows. Treatment is chosen case by case, and scars continue to remodel for months, so progress is reviewed over time. For more on raised scars, see keloid scars, and for scar treatment options, see laser scar removal.

Lighter patches (hypopigmentation) are rare after fractional CO2. They can appear months after treatment, sometimes as a patch with a sharp edge. Some improve over time; others last. Even sun protection helps keep the contrast from widening, and any further treatment is chosen carefully, because options to restore lost pigment are limited.

Breakouts, milia and melasma flares

Small breakouts, tiny white bumps (milia) and flares of melasma can follow CO2 laser, and most settle with simple changes and time. They are usually less serious than infection or scarring, but they should still be mentioned at review.

• Breakouts: heavy ointment and swelling can block pores in the first one to two weeks. Switching to a lighter moisturiser once the doctor allows usually helps. Painful, spreading pustules should be checked for infection.
• Milia: small, firm white bumps that appear as the skin heals. They often clear on their own or can be removed easily by a doctor. Do not squeeze them.
• Contact reactions: an itchy, red rash, sometimes with small bumps, can come from a product applied to the healing skin. Stopping the product and seeing a doctor is the usual step.
• Melasma flares: heat from any laser can worsen melasma. Fractional CO2 is not a melasma treatment, and active melasma usually changes the settings, timing or choice of laser. If melasma darkens after treatment, strict sun protection with tinted SPF and a medical plan are needed, as your doctor will advise.

To lower these risks, mention acne tendency, sensitive skin, melasma and any product reactions at consultation. Use only the products recommended for each stage of healing, and restart actives only when cleared. For guidance on what to use while the skin recovers, see post-laser recovery skincare.

Warning signs: what is normal and when to get help

About a week of redness, swelling, oozing and fine crusts, then fading pinkness, is normal after CO2 laser; rising pain, yellow crusts, pus, clusters of blisters or fever are not. Use the table as a general guide, and contact your provider or a doctor if you are unsure.

Fever, spreading redness with feeling unwell, or any eye pain or change in vision needs urgent medical care.

How Dr Sin Yong assesses and corrects CO2 laser problems

At SkinRev Lab, Dr Sin Yong, medical adviser, assesses CO2 laser problems by examining the skin, identifying what is happening, and reviewing how the treatment was done before planning any correction. The first priority is always to help the skin heal; further treatment comes later, if at all.

What helps the assessment:

• The date of treatment, the area and the number of sessions.
• The device and settings, if you know them, and whether other treatments were combined.
• The aftercare products and any medicines you used.
• Photos taken before treatment and during healing.

What correction may involve, where appropriate:

• Treatment of infection or a cold sore flare, and close wound care.
• A sun-protection and prescription plan for darker patches or melasma.
• Calming care, and later treatment aimed at redness if it persists.
• Silicone, anti-inflammatory treatment or laser for raised scars, timed to healing.
• For remaining texture, a later, conservative session with the DEKA Tetra Pro and the S3 (Stack, Scan, Sculpt) protocol, which is planned for Fitzpatrick III to V skin.

Improvement takes time, and some changes may only partly improve. Dr Sin Yong will explain what is realistic before any plan starts, and correction is priced at consultation. If your treatment was done elsewhere, it is still worth contacting that provider too, as they hold your treatment records.

How to lower the risk: questions to ask before CO2 laser

The most useful way to lower the risk is to have CO2 laser with a doctor who examines your skin and scars first, adjusts settings to your skin type, and gives a clear aftercare and sun-protection plan. These questions help:

• Who performs the laser, and how much experience do they have with fractional CO2 on Asian skin?
• How will settings be adjusted for my skin type, and would more sessions at lower density suit me better?
• What is the plan for my scar type? Some scars do better combined with subcision or other steps.
• What will recovery look like day by day, and when can I return to work and wear make-up?
• Who do I contact if the skin looks wrong, and how quickly will I be seen?

Tell the doctor about: active acne, infection, cold sores, a recent tan or sunburn, keloids or thick scars, poor wound healing, pregnancy, melasma, and recent acne medicines, including oral acne medicine, so timing can be discussed.

Your part after treatment: use only the recommended ointment at first, do not pick, sleep slightly propped up, stay out of direct sun, and use SPF 50 every morning once the skin has closed. Make-up waits until the skin has closed, and gyms and saunas wait until then too.

A doctor who suggests waiting, or a different treatment, is often protecting your skin. For costs, see CO2 laser price, and for how it compares with other options, see pico laser vs CO2 laser.