Quick answer
Dark patches after laser are often post-inflammatory hyperpigmentation: the skin answers heat or injury by making extra pigment, which happens more often in Asian skin and is reduced by daily sunscreen and conservative settings.
- Why: heat and inflammation switch on pigment cells, and richly pigmented skin has more to switch on.
- How often: 7.1 to 12.4 per cent in one fractional laser study of Chinese patients; the rate depends on the laser and the settings.
- Prevent: daily sunscreen was the only measure that consistently worked in a review; density, energy and cooling matter too.
- Treat: usually partial improvement; see a doctor early if a patch darkens, spreads or does not fade.
Why do dark patches appear after laser?
A laser works by heating a target in the skin. The skin also reacts to the heat as an injury, and one of its answers is to make more melanin. This is post-inflammatory hyperpigmentation, and it is more common and more obvious in richly pigmented skin. The article on pigment laser side effects sets out the four named risks, including pale spots and melasma flares.
The same process explains the dark marks left by acne, which is described in the guide to PIE and PIH. For melasma, a laser can add its own heat to a patch that already reacts to heat, as the article on melasma and lasers explains.
How common are dark patches after laser in Asian skin?
Reported rates depend on the laser and the settings, and the numbers are from specific groups. In a Hong Kong study of 37 Chinese patients with 119 sessions of a 1,540 nm fractional laser, generalised PIH occurred in 7.1 per cent after high-energy, low-density treatment and 12.4 per cent after low-energy, high-density treatment, a difference that was not statistically significant. Local PIH around the mouth occurred where no air cooling was used.
A 2025 meta-analysis of 21 studies and 971 people found post-inflammatory hyper- and hypopigmentation much more obvious in Asian than European patients. No source read gives a dependable rate for Malaysian skin or for any single device, and a figure from one laser and one set of settings cannot be moved to another.
Do picosecond lasers cause fewer dark patches than Q-switched lasers?
Studies report that they may. The 2025 meta-analysis found significantly less post-inflammatory hyperpigmentation with picosecond than nanosecond (Q-switched) lasers (P = 0.02) and less hypopigmentation (P = 0.002), while clearance of pigment was comparable for endogenous pigmentation. Its authors note that the safety profile is supported mainly by Asian cohorts and that data for other skin types are sparse.
A smaller trial gives a more cautious picture. A Thai split-face study of 14 adults found more than 50 per cent improvement at six months in 85.7 per cent of picosecond sites against 57.2 per cent of Q-switched sites, with no significant difference in side effects or healing time. Both results describe laser classes, not any one machine, and neither supports saying that a given laser prevents dark patches.
How can dark patches after laser be prevented?
Sunscreen is the step the evidence supports consistently. A systematic review of 14 studies and 369 Asian cases, more than 95 per cent after laser, found sunscreen the only measure that consistently prevented PIH. Topical corticosteroids and tranexamic acid taken by mouth were less successful, which means they are not a substitute.
Settings and technique also matter. In the fractional laser study, density and energy determined the risk, and cooling was important in small areas, although the systematic review linked cooling air devices with worse PIH, so the evidence on cooling is mixed. Practical steps follow from this: a test spot so that the response can be seen before the whole area is treated, no treatment on freshly tanned or inflamed skin, and conservative energy with gaps between sessions. No trial read measured test spots, so they are a sensible step rather than a proven one.
What helps once dark patches have appeared?
Most options give partial improvement, and complete clearing is the exception. The table is from a systematic review of 41 studies and 877 people, most of whom had PIH after acne, so it may not carry over to every cause.
| Approach | Complete response | Partial response | Poor or no response |
|---|---|---|---|
| Topical treatments | 5.4% | 72.4% | 22.2% |
| Lasers and energy devices | 18.1% | 61.2% | 18.1% (and 2.6% worsened) |
| Combinations | 2.4% | 84.9% | 12.7% |
| Chemical peels (15 people) | Not reported | 33.3% | 66.7% |
A second review of 48 studies, 27 per cent of the people Asian, found topical retinoids the most reported choice, with partial improvement in 85 per cent, and laser the only intervention with complete resolution in a subgroup, at 26 per cent, with cases of worsening. Its authors conclude that no modality has robust efficacy across the board. That is why the choice is for a doctor, who weighs the skin, the cause and what could make it worse, and why sunscreen continues throughout.
How long do dark patches after laser last?
There is no single figure. The reviews describe PIH as chronic once it has developed, with a course that varies, and the guide to PIE and PIH gives the reported timescales, from months to years in richly pigmented skin. Pigment that sits deeper in the skin is slower to clear, as that guide explains.
When should I see a doctor about dark patches after laser?
See the treating clinic or a doctor early if a patch is darkening or spreading after the first week or two, if there is blistering, crusting or weeping skin, if pale spots appear, or if the patch matches the shape of the treatment and is not fading. Early advice matters because some treatments for dark patches can irritate the skin and make it worse. A pigmented spot that has changed in size, colour or shape should be examined by a doctor before any further laser.
Who performs PicoSure at The Retreat Clinic in Setia Alam?
Dr Ong performs PicoSure at the clinic. The article on PicoSure sessions, pain and downtime and the PicoSure page set out the treatment. The studies above describe picosecond lasers as a class and do not show that any particular device prevents dark patches.
