Laser Treatment for Acne Scars: Ablative vs Non-Ablative

Fractional lasers are among the more effective tools for indented acne scars, but they soften scars rather than erase them. Ablative fractional lasers (CO2 and erbium) generally give bigger changes with about a week or more of healing, while non-ablative fractional lasers need more sessions but far less downtime. In darker skin, laser type and settings matter a great deal because of the risk of post-inflammatory hyperpigmentation. For active acne, light-based devices such as blue light have weak evidence.

How do lasers treat acne scars?

The American Academy of Dermatology (AAD) explains that laser treatment resurfaces the skin by prompting new collagen and elastin, and can contour the skin around a scar so it looks less noticeable. There are two main families:

• Ablative lasers vaporise thin layers of skin. StatPearls describes the two main types: the CO2 laser (10,600 nm), which goes deeper and tightens more but carries more pigment risk, and the erbium or Er:YAG laser (2,940 nm), which is gentler and heals faster.
• Non-ablative lasers heat tissue below the surface without removing the top layer, so recovery is quicker but more sessions are usually needed (see this evidence review).

Either type can be fractional, meaning the beam is split into microscopic columns that treat only a fraction of the skin at a time, leaving untouched skin in between to speed healing. StatPearls notes this reduces the severity and frequency of complications compared with older full-surface resurfacing.

Ablative vs non-ablative lasers: how do they compare?

What does the evidence show?

Lasers are one of the better-studied scar treatments, but that’s a low bar. The Cochrane review of acne scar interventions (24 trials, 789 people) found fractional lasers were more effective than older non-fractional non-ablative lasers on participant-rated improvement, while fractional radiofrequency performed about as well as fractional laser, and chemical peels performed similarly too. Certainty ranged from very low to moderate, and the review did not support any single treatment as first-line.

A 2023 network meta-analysis of six energy-based devices (11 studies, 405 patients) ranked Nd:YAG, fractional CO2 and Er:YAG highest for effectiveness, and radiofrequency-based devices lowest for hyperpigmentation risk, with fractional CO2 the highest. The authors cautioned that the ranking rests on small samples with few direct comparisons.

Scar type matters too. StatPearls notes raised and shallow boxcar scars respond best to laser, while ice pick scars usually need a second treatment such as TCA CROSS. It also reports that older non-ablative lasers improved atrophic scars by about 40 to 45% after roughly three monthly sessions. For how lasers stack up against the alternatives, see acne scar treatments and microneedling for acne scars.

Can lasers treat raised scars and red marks?

Yes, but with different lasers from the resurfacing ones above. For raised scars, the AAD lists lasers among the options for hypertrophic scars and says dermatologists use lasers for small raised papular scars. StatPearls describes the pulsed dye laser (585–595 nm) as the most common option for hypertrophic scars and keloids, reporting 57 to 83% improvement in the appearance and texture of hypertrophic scars after 1 to 2 treatments. Keloids are usually treated with a combination, such as laser plus steroid injections.

Flat pink or red marks after acne (post-inflammatory erythema, or PIE) are not scars, and they tend to fade over time. A short 2013 report in the Journal of Clinical and Aesthetic Dermatology describes using a 595 nm pulsed dye laser for these marks, but its evidence is case examples rather than trials. Flat brown marks need a different approach; see post-inflammatory hyperpigmentation.

Are lasers safe for darker skin?

They can be, with the right device and cautious settings, but this is where experience matters most.

• StatPearls says non-fractional CO2 resurfacing is not recommended for skin types IV and above, and that Er:YAG is preferred over CO2 for darker skin.
• A review of non-ablative fractional lasers in skin of colour reports hyperpigmentation in 0.73% of 961 consecutive treatments across skin types I to V, more often in skin of colour, with risk climbing as treatment density rose. It recommends lower densities, more sessions and longer gaps between treatments, while noting that more studies in skin types V and VI are “sorely needed.”
• StatPearls cites a study in skin types III to V in which 45.5% developed temporary hyperpigmentation after laser treatment, which resolved within 3 months in 90% of those affected.

Microneedling is often suggested as a lower pigment-risk alternative for darker skin. Whatever you choose, ask how many people with your skin tone the provider has treated with that exact laser.

What should you expect before and after laser treatment?

The AAD’s advice on laser scar treatment sets realistic expectations: a laser “can make a scar less noticeable, but it cannot get rid of a scar,” results depend heavily on the operator’s skill, and it can take months to see results. It also recommends:

• Not arriving tanned or sunburned, since your dermatologist cannot treat you.
• Stopping smoking for at least 2 weeks beforehand, and avoiding aspirin, vitamin E, retinoids and glycolic acid before treatment as advised.
• Expecting more than one session, especially with non-ablative lasers, and possibly a combination with fillers or other treatments.
• Budgeting for it: insurers consider laser scar treatment cosmetic.

Two more medical points to raise. StatPearls says antiviral medicine is recommended around ablative resurfacing to prevent cold sore flare-ups, and that traditional teaching was to wait 6 to 12 months after isotretinoin (see isotretinoin). Afterwards, the AAD advises daily SPF 30+ broad-spectrum, water-resistant sunscreen and limiting sun exposure for 6 to 8 weeks.

Do lasers and light therapy help active acne?

Much less convincingly than for scars. According to the AAD, blue, red and blue-plus-red light can treat pimples but not blackheads, whiteheads, cysts or nodules; multiple sessions work better than one; and these treatments rarely clear acne on their own. Home light devices are weaker, and some need to be used for 30 to 60 minutes twice a day for 4 to 5 weeks with unpredictable results. Photodynamic therapy (a light-activated solution plus light) looks more promising for severe acne, but requires avoiding sunlight for 48 hours afterwards.

The Cochrane review of light therapies for acne pooled 71 studies with 4,211 participants and concluded that high-quality evidence is lacking, rating most comparisons as very low certainty. The AAD’s 2024 acne guideline likewise found evidence insufficient to make recommendations for laser and light-based devices. So light therapy is an optional extra for people who can’t use or don’t respond to standard treatments, not a first step. The AAD notes lasers and light therapies are considered relatively safe in pregnancy but advises seeing a dermatologist first (more in pregnancy-safe acne treatment).

Frequently asked questions