Laser treatment for pigmentation which laser for which pigment, and how to avoid rebound darkening

How it works

How laser pigmentation removal works

Every pigment laser relies on one principle, selective photothermolysis. Light of a chosen wavelength passes through the skin and is absorbed mainly by melanin, and each pulse is short enough that the energy stays in the pigment instead of spreading to the skin around it. The pigment breaks into fragments, and the skin's clean-up cells carry them away over the following weeks.

Three settings decide what a laser can do. Wavelength sets the target and the depth: 532 nm is absorbed strongly by brown pigment near the surface, 755 nm and 785 nm sit in between, and 1064 nm passes deeper with less absorption by the skin surface, which is gentler on darker skin. Pulse length sets how the pigment breaks: millisecond (long-pulsed) lasers heat it, nanosecond (Q-switched) lasers fracture it, and picosecond lasers shatter it mainly with a pressure wave. Energy and spot size set how hard the skin is pushed.

Depth matters as much as darkness. A review of pigment disorders in Asian patients describes melasma, freckles and sun spots as common pigment in the epidermis, Hori's naevus as a common one in the dermis, and darkening after any skin injury as a hallmark of skin of colour. The same review points out a trade-off: Q-switched lasers work well on epidermal pigment but come with a high risk of that darkening, whereas gentler long-pulsed options carry less risk but take more sessions.

Matching

Laser treatment for pigmentation: which laser for which pigment

This is the usual starting point once a doctor has confirmed what each mark is. Many faces carry more than one type, such as sun spots sitting on top of melasma, and then each is treated differently, sometimes in a different order.

Anything raised, waxy, changing, bleeding or irregular is examined first. Some skin cancers look like ordinary brown spots, and a laser should never be used on a lesion that has not been checked.

Sun spots and freckles

Sun spots and freckles: where pigment lasers work fastest

Flat, well-defined sun spots and freckles sit near the surface, so they are the pigment that lasers clear most readily. In a prospective study of 20 Asian women with skin types III and IV, a 532 nm picosecond laser cleared 40 of 43 sun spots by more than 75% after a single session; the other three needed a second, and PIH followed in under 5% of the treated spots.

The choice of laser still matters in Asian skin. A retrospective study of 40 Chinese patients treated with four different pigment lasers found that the long-pulsed alexandrite group did not improve significantly and that 20% of those patients developed PIH, against 10% after Q-switched 532 nm laser and none after two other long-pulsed lasers. The authors concluded that long pulses with small spot sizes lower the risk. Small studies like these guide settings; they do not settle which machine is right for your skin.

At IN Eternity Clinic, Dr Sin Yong chooses between the Alexandrite Laser for flat, defined spots, the 532 nm and 785 nm outputs of Pico Laser, and the R2 Glow course on the Fotona StarWalker for scattered, sun-related pigment. Treated spots usually look darker for a few days before they flake; after the Alexandrite Laser the fine crusts take about one to two weeks to clear. Freckles and new sun spots return with sun, so occasional touch-ups are common.

Melasma

Melasma: why low-fluence toning comes with caution

Melasma is driven by UV, visible light, heat and hormones, so it is managed rather than cured. Laser can lighten it, but strong heat-based pigment lasers, such as long-pulsed alexandrite, can make it darker, which is why melasma is treated with low energy or not lasered at all.

Laser toning passes a 1064 nm Q-switched Nd:YAG at low energy across the face over a course. Across 42 studies, a systematic review judged it generally effective and safe for melasma, particularly in Asia, while flagging three problems: persistent pale, mottled patches when too much energy accumulates, darkening when it is used aggressively on darker skin, and a shortage of long-term results. In a Hong Kong case series, 14 Chinese women developed mottled depigmentation after 6 to 50 toning sessions, some after only a few, and toning did not significantly improve melasma in any of the five treated for it.

So a doctor usually starts with, or pairs laser with, prescription treatment such as hydroquinone cream or tranexamic acid tablets, strict sun protection and toning sessions spaced a few weeks apart. At IN Eternity Clinic these medicines are prescribed by Dr Sin Yong after a consultation when appropriate; SkinRev Lab does not prescribe. Take care with lightening creams sold online; Singapore's Health Sciences Authority has issued warnings about creams found to contain mercury, and hydroquinone is available here only on prescription.

Deeper pigment

Hori's naevus and café-au-lait spots: slower, less predictable

Hori's naevus, also called acquired bilateral naevus of Ota-like macules (ABNOM), is blue-grey or grey-brown speckling on both cheekbones, appearing in adulthood and most common in East Asian women. The pigment sits in the dermis, so creams and peels do little. A 2026 meta-analysis of 40 mostly small studies found no significant difference between picosecond and Q-switched lasers in reaching at least 75% clearance (about 48% and 53% in pooled estimates), while each extra session was linked with about three times the odds of clearance. The evidence was rated very low certainty, and temporary darkening for some weeks after each session is common.

Café-au-lait spots are birthmarks: flat, light brown and the same shade all over. One or two are common and harmless, but six or more spots larger than 5 mm in a child before puberty is one of the criteria for neurofibromatosis type 1, so a child with several spots, new spots, or freckles in the armpits or groin should see a GP, paediatrician or dermatologist before any cosmetic decision.

For adults who want a spot lighter, results are less predictable than for sun spots. A 2023 meta-analysis of 19 studies and 991 patients found that about three in four reached at least 50% clearance and about four in ten reached 75%, with recurrence averaging around 13%; the Q-switched 1064 nm group had the lowest rates of darkening and lightening. A test patch on part of the spot comes first.

Asian skin

PIH and rebound darkening in Asian skin

Post-inflammatory hyperpigmentation is the skin's habit of making extra pigment after heat or inflammation. Asian skin does this readily, so the laser that clears a spot can leave a brown shadow around it for weeks or months. In the studies above, PIH followed under 5% of sun spots treated with a 532 nm picosecond laser, but 10 to 20% of patients treated with some other pigment lasers.

Rebound is the melasma version: pigment returns darker after treatment, usually when energy, frequency or heat is too high. Over-treatment can also go the other way and leave pale, mottled patches that are harder to fix than the original pigment.

Post-acne marks are themselves PIH. Many fade over months once breakouts are controlled and the skin is protected from sun, so laser is kept for marks that linger, using gentle toning or picosecond passes rather than strong heat.

• A diagnosis before any laser, because a laser chosen for the wrong pigment can darken it.
• No treatment while tanned or sunburnt; wait for the tan to fade.
• Conservative energy at the first session, with cooling, then adjustment.
• Sessions spaced to let the skin settle, rather than packed close together.
• Strict sun protection between sessions, and early reporting of any new darkening or pale patches.

Test patches

Why a test patch often comes first

A test patch means treating a small, representative area at the planned settings, then waiting, usually a few weeks, to see whether it lightens, darkens or stays the same before the rest is treated. Darkening after laser usually shows within those first weeks, so a short wait can prevent a whole cheek of it.

It is most useful when the response is hard to predict: skin that tans easily or has darkened after spots, insect bites or earlier treatments; café-au-lait spots; mixed pigment such as sun spots over melasma; and anyone starting a new laser or wavelength. It is not a promise that the full treatment will behave the same way, but it is the most practical guide available.

• Have every mark diagnosed first, and any spot that is new, changing, raised, bleeding or irregular examined before laser.
• Mention past darkening after acne, eczema, bites, waxing or earlier lasers.
• Expect conservative settings at the first session.
• Take photos in the same light at each visit, so changes are judged fairly.

Sessions and downtime

How many sessions, and what each one looks like

Session numbers are the part of pigment treatment most people underestimate. The figures below come from studies and clinical practice; they are patterns, not a plan for your skin.

Aftercare

Aftercare in Singapore's sun and humidity

The sun that made the pigment keeps prompting more, and Singapore's UV index stays high through the year. Aftercare is mostly about protecting the treated skin while it renews, and about not undoing the work between sessions.

• Leave darkened spots and fine crusts to fall off on their own; picking raises the chance of marks.
• Cleanse gently, moisturise, and skip scrubs, exfoliating acids and retinoids on the area until the skin has settled, or as advised.
• Wear broad-spectrum sunscreen, SPF 30 or higher, every day and top it up outdoors; for melasma, a tinted formula with iron oxide adds protection against visible light.
• Take extra care between 11am and 3pm, with shade, a broad-brimmed hat and an umbrella.
• For melasma, limit heat as well as sun, since heat is one of its triggers.
• Plan sessions away from beach holidays, and report any new darkening or pale patches early.

Where to go

Laser pigmentation removal in our network

Pigment lasers are medical treatments performed by doctors. Dr Sin Yong treats pigment at IN Eternity Clinic, 9 Scotts Road, #12-01 Pacific Plaza, beside Orchard MRT, after looking at it closely, often under magnification, and then picks from four lasers: Pico Laser (T2 Frax Radiance) on the DEKA TORO, with a 785 nm picosecond output and 532 nm and 1064 nm Q-switched outputs; Laser Toning with a low-fluence 1064 nm Q-switched Nd:YAG; the Alexandrite Laser, 755 nm long-pulsed, for flat, defined spots; and R2 Glow Laser, a gentle course on the Fotona StarWalker. All are priced at consultation by the clinic, open Monday to Saturday, 11am to 8pm; WhatsApp +65 8815 3008.

There are no lasers at SkinRev Lab, the non-invasive aesthetic centre at CityLink Mall #B1-28 between City Hall and Esplanade MRT; laser enquiries made there are passed to the clinic. Between laser courses, for dullness and mildly uneven tone, its Needleless SkinBooster costs S$288 per region before GST, with the first region from S$98. It supports tone and hydration but does not remove defined spots or treat melasma.

Sources

References & sources

1. Ho SG, Chan HH. The Asian dermatologic patient: review of common pigmentary disorders and cutaneous diseases. Am J Clin Dermatol. 2009;10(3):153-168.
2. Negishi K, Akita H, Matsunaga Y. Prospective study of removing solar lentigines in Asians using a novel dual-wavelength and dual-pulse width picosecond laser. Lasers Surg Med. 2018;50(8):851-858.
3. Ho SG, Chan NP, Yeung CK, Shek SY, Kono T, Chan HH. A retrospective analysis of the management of freckles and lentigines using four different pigment lasers on Asian skin. J Cosmet Laser Ther. 2012;14(2):74-80.
4. Lee YS, Lee YJ, Lee JM, Han TY, Lee JH, Choi JE. The low-fluence Q-switched Nd:YAG laser treatment for melasma: a systematic review. Medicina (Kaunas). 2022;58(7):936.
5. Chan NP, Ho SG, Shek SY, Yeung CK, Chan HH. A case series of facial depigmentation associated with low fluence Q-switched 1,064 nm Nd:YAG laser for skin rejuvenation and melasma. Lasers Surg Med. 2010;42(8):712-719.
6. Li F, Wang Y, Shen Z. Efficacy of Q-switched and picosecond lasers for acquired bilateral nevus of Ota-like macules: a systematic review and exploratory dose-response meta-analysis. Lasers Med Sci. 2026;41(1):180.
7. Guo ZZ, Wang ZC, Wang D, et al. Laser treatment for cafe-au-lait macules: a systematic review and meta-analysis. Eur J Med Res. 2023;28(1):185.

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