CO2 Laser Resurfacing Side Effects: 8 Things Patients Are Not Always Told

Redness after CO2 laser resurfacing is universal, every patient will experience it to some degree. It is a normal inflammatory response as the skin begins repairing itself following treatment. What surprises many patients is how long it can last.

With fractional CO2 laser: Intense redness typically resolves within 3 to 5 days. However some redness or pinkness can persist for 2 to 4 weeks depending on treatment depth. Between 5 and 15% of patients still have visible pinkness at week 8.

With fully ablative CO2 laser: Redness is significantly more intense and longer lasting. Research confirms redness can persist for 3 to 6 months, particularly in fair skin after deep treatment settings. This is one of the most commonly underestimated aspects of fully ablative recovery.

Who is most affected: Fair-skinned patients, those who have had deeper treatment settings, and those who have full-face rather than targeted treatment.

What influences how long redness lasts: Sun exposure without adequate SPF is the most significant factor. Even brief unprotected sun exposure during recovery can significantly prolong redness. Strict SPF use is not optional during the recovery period, it is essential.

When redness becomes a warning sign: If redness is spreading beyond the treated area, worsening rather than improving, or accompanied by heat, pain or discharge, contact your practitioner immediately as these can indicate infection.

Swelling is a universal side effect of CO2 laser resurfacing and represents the body’s inflammatory response to the controlled skin injury caused by the laser. Most patients are aware they will swell. Fewer are prepared for where the swelling concentrates.

With fractional CO2 laser: Swelling typically peaks within 24 to 48 hours of treatment and resolves within 3 to 5 days. It is usually mild to moderate.

With fully ablative CO2 laser: Swelling is more pronounced and peaks similarly at 24 to 48 hours but can take 5 to 7 days to resolve. Swelling around the eyes in particular can be significant where some patients find it difficult to open their eyes fully in the first 24 hours after aggressive periorbital treatment.

Who is most affected: Patients undergoing full-face treatment, those with treatment near the eye area, and those with deeper settings.

What helps: Sleeping with the head elevated on extra pillows in the first few nights after treatment significantly reduces facial swelling. Cold compresses applied gently can also help in the first 24 hours. Ask your practitioner for specific guidance before treatment.

When swelling becomes a warning sign: Swelling that worsens after day 2 rather than improving, or that is accompanied by significant pain, heat or spreading redness, warrants urgent contact with your practitioner.

Peeling and crusting after CO2 laser resurfacing is not a complication — it is a normal and expected part of the healing process as the treated skin sheds and new skin regenerates beneath. Understanding what normal peeling looks like prevents patients from interfering with healing unnecessarily.

With fractional CO2 laser: Patients typically notice what practitioners describe as micro-crusting which are tiny brown specks or a sandpaper-like texture rather than sheets of peeling skin. This begins around days 3 to 5 and resolves within 7 to 10 days.

With fully ablative CO2 laser: Peeling is more dramatic. The skin may weep, ooze and form significant crusting in the first 5 to 10 days. This can feel alarming but is a normal response to deeper skin removal. Weeping and oozing typically resolve within the first week.

The single most important rule: Do not pick, peel or scratch the skin during recovery under any circumstances. Removing skin before it is ready to shed naturally significantly increases the risk of scarring and pigmentation changes.

What influences healing: Keeping the skin clean and well moisturised with the products your practitioner recommends speeds healing. Thick occlusive ointments are often recommended in the early days to prevent the skin from drying out.

When peeling becomes a warning sign: If skin is not healing at all after 10 to 14 days, or if new areas of raw skin are appearing rather than healing progressing, contact your practitioner.

The sensation during and immediately after CO2 laser resurfacing is consistently described as similar to a severe sunburn, a warm, tight, stinging feeling that varies in intensity depending on treatment depth.

With fractional CO2 laser: Discomfort during treatment is managed with topical numbing cream applied 30 to 60 minutes before. The sunburn sensation typically persists for 1 to 3 days after treatment and is manageable with over-the-counter pain relief as advised by your practitioner.

With fully ablative CO2 laser: Discomfort is significantly more intense and longer lasting. Local anaesthetic or sedation is typically used during the procedure itself. The post-treatment sunburn sensation can persist for 7 to 14 days and may require prescribed pain relief rather than over-the-counter options.

Who experiences more discomfort: Patients undergoing deeper treatment settings, full-face treatment, or treatment near more sensitive areas including the lips and eye area.

When pain becomes a warning sign: Pain that is significantly worsening rather than improving after day 3 to 4, or that is accompanied by fever, spreading redness or discharge, should prompt immediate contact with your practitioner as these can signal infection.

Milia are small white or yellow cysts that can appear on the treated skin in the weeks following CO2 laser resurfacing. They are one of the most common side effects that patients are not adequately warned about before treatment, affecting approximately 17% of patients.

How they develop: Milia typically appear between 4 and 8 weeks after treatment. They develop when the thick occlusive ointments used during recovery — essential for keeping the healing skin moist — temporarily clog pores and trap dead skin cells beneath the surface.

The difference between fractional and fully ablative: Both treatments carry a risk of milia but the risk is higher after fully ablative resurfacing where heavier aftercare products are required for longer.

What to do: Most milia resolve on their own without intervention as the skin continues to normalise. Some require gentle extraction by a practitioner. Do not attempt to squeeze or extract them yourself as this can cause scarring or infection.

What reduces the risk: Transitioning to lighter moisturisers as soon as your practitioner advises it, rather than continuing heavy occlusive products beyond the initial healing phase.

Some patients experience an acne flare in the weeks following CO2 laser resurfacing, typically appearing between 2 and 4 weeks after treatment as oil production in the skin rebounds following the trauma of the procedure.

Who is most affected: Patients with a history of acne are at higher risk. However acne flares can occur in patients with no prior acne history.

The difference between fractional and fully ablative: Both treatments carry this risk. The occlusive aftercare required after fully ablative resurfacing can increase the likelihood of breakouts.

What to do: A mild post-treatment acne flare is temporary and typically resolves as the skin normalises and you return to your regular skincare routine. Contact your practitioner if the breakout is significant or appears to be spreading, as they can advise on safe topical treatments during the recovery period.

What reduces the risk: Transitioning away from heavy aftercare products as soon as it is safe to do so, and resuming normal skincare gradually under practitioner guidance.

Pigmentation changes are one of the most significant potential side effects of CO2 laser resurfacing and one of the most important to understand before committing to treatment, particularly for patients with medium to dark skin tones.

Post-inflammatory hyperpigmentation (PIH): The treated area darkens as the skin produces excess melanin during healing. This affects between 15 and 30% of patients overall, with significantly higher rates in patients with Fitzpatrick skin types III to VI. PIH is usually temporary and can be treated with topical agents including hydroquinone over a period of 2 to 4 months. Significant PIH in darker skin types can take 6 to 12 months to fully clear.

Hypopigmentation: The treated area develops lighter patches where melanocyte damage has occurred. Hypopigmentation is less common than hyperpigmentation but carries a more serious risk profile and it can be permanent. It is more likely with deeper fully ablative treatment settings.

The difference between fractional and fully ablative: Fractional CO2 laser carries a lower risk of pigmentation changes than fully ablative resurfacing because surrounding skin is preserved. Fully ablative treatment carries a higher risk, particularly for PIH in patients with Fitzpatrick types III to VI, and for permanent hypopigmentation in patients of any skin type if treatment settings are too aggressive.

What significantly reduces the risk: Strict sun avoidance and high-SPF sunscreen throughout the recovery period. A pre-treatment skincare protocol including retinoids and hydroquinone, prescribed by an experienced practitioner, can also reduce PIH risk in higher-risk skin types.

Who should be particularly cautious: Patients with Fitzpatrick skin types III to VI should only proceed with CO2 laser resurfacing after a thorough skin assessment by a practitioner with specific experience treating darker skin tones. Fractional CO2 laser is generally more appropriate than fully ablative resurfacing for these skin types.

Choosing a practitioner with specific experience treating patients with higher Fitzpatrick skin types is essential. Find verified CO2 laser clinics in London, Manchester and Birmingham.

This is one of the most important side effects in this guide and one that patients with a history of cold sores frequently are not adequately warned about before treatment.

CO2 laser resurfacing around the mouth and across the face can reactivate the herpes simplex virus in patients who carry it.  This can often causing a cold sore outbreak during the recovery period. Because the skin barrier is already compromised during healing, a herpes outbreak during CO2 laser recovery can spread rapidly and cause significant complications including scarring.

The difference between fractional and fully ablative: Both types of CO2 laser carry this risk for patients with a history of cold sores. The risk is higher with fully ablative resurfacing and with perioral (around the mouth) or full-face treatment.

The solution: Prophylactic antiviral medication prescribed before treatment. Any patient with a history of cold sores should inform their practitioner before treatment and be prescribed antivirals to take from the day before treatment through the recovery period. This is standard practice at reputable clinics.

What to do if you have a history of cold sores: Tell your practitioner at your consultation. If they do not raise antivirals proactively, ask directly. A practitioner who is unaware of this risk or does not prescribe prophylactic antivirals is a significant warning sign.

Before your consultation, use our questions to ask at your CO2 laser consultation to make sure you are asking the right things.

Understanding the distinction between expected healing and genuine complication is the most important practical knowledge to take into a CO2 laser consultation.

Normal recovery:

• Redness, swelling and peeling resolving gradually over days to weeks
• Micro-crusting that sheds naturally without intervention
• Mild discomfort that improves day by day
• Milia appearing at weeks 4 to 8 and slowly resolving
• Mild acne flare resolving as skincare normalises

Contact your practitioner promptly if:

• Redness is spreading beyond the treated area
• Redness, pain or swelling is worsening after day 3 to 4 rather than improving
• You develop a fever
• There is yellow or green discharge from the treated area
• Blistering is appearing in unexpected areas
• There is no healing progress after 10 to 14 days
• You experience significant eye irritation or difficulty fully opening your eyes

Seek urgent medical attention if:

• You have signs of a systemic infection including fever above 38 degrees, chills, or spreading skin redness
• You experience vision changes after treatment near the eye area
• You have a herpes outbreak and were not prescribed antivirals

Every CO2 laser clinic listed on The Aesthetic Standard is manually reviewed by our editorial team before being included. We check:

Statutory medical registration: General Medical Council (GMC) for doctors, General Dental Council (GDC) for dentists, Nursing and Midwifery Council (NMC) for nurses. For non-medically registered practitioners: Ofqual-regulated Level 4 qualification in Laser and IPL at minimum and a named medical oversight arrangement. Professional body membership: British College of Aesthetic Medicine (BCAM) or British Association of Medical Aesthetic Nurses (BAMAN). Care Quality Commission (CQC) registration where held. Local authority licensing where required. Voluntary accreditation with Save Face or the Joint Council for Cosmetic Practitioners (JCCP). Professional indemnity insurance specifically covering CO2 laser treatment. Independent patient feedback across Trustpilot and Google. Where possible we speak directly with patients who have undergone treatment at the clinic.

A listing on The Aesthetic Standard is not a guarantee of outcome. It is confirmation that the clinic has met our verification criteria and that the practitioner holds the appropriate statutory registration and professional credentials to perform the treatment safely. Read our full verification criteria before choosing a clinic.

Before your consultation, use our questions to ask at your CO2 laser consultation to make sure you are asking the right things.

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For the full breakdown of CO2 laser results and what to expect, read our CO2 laser before and after guide. For the complete guide to both treatment types, visit our fractional CO2 laser guide and ablative CO2 laser guide or our full CO2 laser treatment guide.

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