Laser pigmentation treatment: matching the laser to the pigment

Brown facial spots can represent freckles, solar lentigines, melasma, post-inflammatory hyperpigmentation, seborrhoeic keratoses, birthmarks or — in uncommon cases — something that should not be treated cosmetically at all.

A fourth that is frequently missed

Hori's naevus (acquired bilateral naevus of Ota-like macules) produces speckled blue-grey pigmentation over the cheekbones and is commonly mistaken for melasma in Asian patients. It sits deeper in the skin, responds to different treatment, and will not improve on a melasma regimen — so months can be spent treating the wrong diagnosis. Pigment that looks more grey than brown, and speckled rather than diffuse, is worth flagging specifically.

Pigment lasers work because melanin absorbs selected wavelengths. Shorter visible wavelengths can target superficial pigment strongly, while 1064 nm Nd:YAG penetrates more deeply and is absorbed less avidly by epidermal melanin. Picosecond and Q-switched systems deliver very short pulses intended to fragment pigment with limited heat spread.

Picosecond systems are heavily marketed, and it is worth being clear about what the shorter pulse does. It fragments pigment with less heat spread into surrounding tissue, which is a genuine advantage for reducing thermal injury. It does not make the device suitable for a diagnosis it was never suited to — a picosecond laser used on melasma can still aggravate it.

Skin with more active melanocytes can darken after inflammation. That means aggressive fluence, unnecessary overlap, recent tanning, active irritation and inadequate sun protection can turn a treatment for pigmentation into new pigmentation.

Test spotting is worth asking for explicitly. Treating a small, discreet area first and reviewing it several weeks later costs one extra visit and reveals how your skin actually responds before the whole face is committed. Where pigmentation risk is significant, that is a considerably better trade than discovering the response afterwards.

Melasma tends to recur because the underlying tendency remains. Daily broad-spectrum sunscreen, visible-light protection where appropriate, topical pigment control and trigger management usually form the foundation. Lasers may have a role in selected cases, but repeated or aggressive treatment can aggravate the condition.

Two triggers are routinely overlooked in Singapore. Visible light — ordinary daylight, not just UV — drives melasma in darker skin types, which is why a tinted sunscreen containing iron oxides outperforms a clear one here. And heat: cooking over a stove, hot yoga, saunas and ambient humidity can aggravate melasma independently of light exposure. Patients who cannot explain a flare often find the answer in one of these rather than in sun exposure.

Tranexamic acid, hydroquinone and other prescription approaches have specific contraindications and should be selected medically rather than used as generic post-laser add-ons.

This happens often enough to deserve its own section. The usual causes are identifiable and largely avoidable.

• Wrong diagnosis — melasma treated as though it were sun spots.
• Excessive energy — more reaction mistaken for more effect.
• Treating tanned skin — raised epidermal melanin competes for absorption and raises burn and pigment risk.
• Sessions too close together — inflammation stacking before the previous response has settled.
• Inadequate sun protection afterwards — particularly through the two-to-six-week window.
• Ongoing untreated trigger — active acne, irritation from actives, or heat exposure continuing throughout.

Rebound darkening after apparent initial clearing is the classic pattern in melasma, and it is why a treatment that seemed to work brilliantly at two weeks can look worse at two months.

Discrete spots can temporarily darken before fading or flaking. Redness and mild swelling are common. The final result should be assessed after the inflammatory phase has settled rather than the next morning.

• Use broad-spectrum sunscreen consistently — tinted if you are melasma-prone.
• Avoid deliberate tanning and excessive UV exposure.
• Keep skincare gentle until irritation resolves.
• Do not pick crusted or darkened spots.
• Report blistering, marked pain or unexpected colour change.

The temporary darkening of treated spots is expected rather than a complication. Picking or scrubbing that crust is one of the more reliable ways to convert a good result into a pigmented one.