Lasering sun spots before the light treatment
Laser resurfacing and laser-assisted PDT for actinic keratoses: a review
Photodynamic therapy struggles with thick, crusted sun spots because the cream cannot get through them. Running a fractional laser over the area first opens channels for it — and across a series of trials that combination clears more, recurs less and improves the look of sun-damaged skin more than the light treatment alone.
Four numbers worth knowing
What we found
The problem being solved is penetration, not potency.
Photodynamic therapy is recommended first line for multiple actinic keratoses, with clearance of 69–93% on face and scalp and 24% recurrence at twelve months. Its main weakness is thicker Grade II–III lesions, where the photosensitising cream cannot penetrate the crust — which is why practice has been to curette thick lesions beforehand.
A laser pass first consistently improves clearance.
In a randomised trial, three-hour laser-assisted PDT cleared 91.7% against 76.8% for two-hour laser-PDT and 65.6% for conventional PDT, with the difference still significant at twelve months. In a 15-patient split-face study, laser-PDT cleared 100% of Grade I lesions against 80%, and 88% of Grade II–III against 59%.
Recurrence falls too, which matters more than first clearance.
Recurrence at twelve months was 7.5% after three-hour laser-PDT against 22.1% after conventional PDT. Several studies also reported improved photoageing alongside the lower recurrence, with no serious adverse effects beyond mild itch and redness.
It also shortens the waiting around.
Laser pretreatment lets the cream work faster. One study found no significant difference between two-hour laser-PDT and conventional three-hour PDT (71.4% vs 64.7%). Another cleared 70.6% of lesions within three sessions using only 70–90 minutes of incubation.
Density of the laser matters, and more is better here.
In 47 patients randomised to Er:YAG fractional laser at 5.5%, 11% or 22% density before PDT, the 22% density group cleared significantly more at three months (88.7% vs 80.0%) and at twelve (81.1% vs 60.9%), with lower recurrence and no difference in side effects or cosmetic outcome.
For darker skin, the choice of laser changes.
Er:YAG is more appropriate than CO₂ in darker skin types because it causes less thermal damage, heals faster and produces less redness, swelling and post-inflammatory pigmentation. In 45 Korean patients, laser-PDT cleared 86.9% against 61.2% at twelve weeks and recurred less at 48 weeks (9.7% vs 26.6%), with over 90% rated good or excellent cosmetically — though redness and pigmentation were more common in the laser group.
Not every laser helps, and one clearly did not.
Fractional 1927 nm thulium combined with PDT was no better than PDT alone in a 12-patient study of the décolletage, and pulsed-dye laser-assisted PDT was actually inferior to conventional PDT in a 60-patient split-face trial, clearing 10.3% against 44.9% at six months. The combination is not automatically beneficial.
The lip is a harder problem than the face.
Actinic cheilitis is more likely than actinic keratosis to progress to squamous cell carcinoma, and PDT works less well on it — light penetrates the lip unevenly and saliva dilutes the cream. One study found a single session of Er:YAG laser-PDT beat two sessions of conventional PDT, with histological clearance of 92% against 59% at three months and 85% against 29% at twelve.
Guidelines have not caught up, and the review says so.
Despite these results, current guidelines do not recommend laser resurfacing as a primary treatment for actinic keratoses, because the studies are small and lack large placebo-controlled replication. Canadian and European guidelines suggest resurfacing lasers for clustered lesions; British guidelines give a level B recommendation.
What this means for you
Thickness is what decides whether laser is worth adding
The benefit comes from getting the photosensitiser through crusted lesions. For thin Grade I lesions, conventional or daylight PDT already does well.
Daylight PDT is the gentler route where it suits
Applied without occlusion and activated by two hours outdoors, it was non-inferior to conventional PDT at twelve weeks in two split-face trials, and is almost painless — an option for Grade I and II lesions on face and scalp.
Ask which laser, not just whether
Er:YAG and CO₂ both help; thulium and pulsed-dye did not in the studies here, and pulsed-dye was worse than PDT alone. In darker skin, Er:YAG is the safer of the two that do work.
Why this matters
Actinic keratoses are the visible part of a larger problem: the skin around each one carries the same ultraviolet damage, which is why field treatments exist at all. Photodynamic therapy is very good at treating a field, and frustratingly weak where the lesions are thickest — precisely the ones that most warrant treating.
This review gathers what has actually been tested about putting a laser through the skin first. The finding is encouraging but not uniform: some laser pairings clearly improve clearance and reduce recurrence, and at least two do not. Setting out which is which seemed more useful than a general claim that combining them is better.
Why it matters to you
If you have had photodynamic therapy and the thicker, crusted spots came back while the flat ones cleared, that is the known weakness of the treatment rather than a failure of your skin. Adding a laser pass beforehand is the documented answer to it.
What this study cannot tell you
Every study has a boundary, and it is fairer to state it than to leave you to guess.
- This is a review of published trials, not new research, and the underlying studies vary in laser type, settings, incubation time and follow-up.
- Many of the studies are small — several under 30 patients — and split-face designs, which limit how far the results generalise.
- Guidelines do not currently recommend laser resurfacing as a primary treatment for actinic keratoses, and the review says so explicitly.
- Two combinations tested — thulium laser and pulsed-dye laser with PDT — showed no benefit or were inferior to PDT alone.
- Adding laser increases redness, crusting and, in darker skin, post-inflammatory pigmentation compared with PDT alone.
Questions people actually ask
What is photodynamic therapy?
A cream is applied to sun-damaged skin and left to absorb. It concentrates in abnormal cells, and shining a specific colour of light onto the area then activates it, destroying those cells while largely sparing normal skin.
It is recommended first line for multiple sun spots because it treats a whole area at once, including damage not yet visible.
Why would a laser be used before it?
Because the cream cannot penetrate thick, crusted lesions — which is exactly where the treatment otherwise underperforms. A fractional laser creates microscopic channels that let it through.
Across the trials in this review, that combination cleared more lesions and recurred less than the light treatment alone, and also improved the appearance of the surrounding sun damage.
Is it suitable for darker skin?
Yes, with the right laser. Er:YAG is preferred over CO₂ in darker skin types because it causes less thermal damage, heals faster and produces less post-inflammatory pigmentation.
In a study of 45 Korean patients, the laser-assisted group cleared substantially more and recurred less, with over 90% rating the cosmetic result good or excellent — though redness and pigmentation were still more common than with the light treatment alone.
Does adding a laser always make it better?
No, and that is one of the more useful findings here. Er:YAG and CO₂ pretreatment improved results consistently.
Fractional 1927 nm thulium added nothing over PDT alone, and pulsed-dye laser pretreatment was actually worse than conventional PDT — 10.3% clearance against 44.9% at six months in a 60-patient trial.
Cite this paper
Lim A, Lim D, Jibreal H. Laser resurfacing and laser-assisted PDT for actinic keratoses: a review. Opinions and Progress in Cosmetic Dermatology. 2022;2(1):28–37.
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Published 2022 · Summary written and reviewed by Dr Davin Lim, FACD · General information, not personal medical advice.
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