What this mark is
Post-inflammatory hyperpigmentation, or PIH, is pigment produced where skin was inflamed. Acne is a common trigger. So are picked spots, insect bites, eczema, friction, shaving, waxing and small cuts. Laser or a peel can cause it too.
It is common in Fitzpatrick III to V skin, which covers most people in Singapore. Depth decides the course. Brown marks sit nearer the surface and tend to fade sooner. Grey or slate marks mean pigment has dropped into the dermis. These are slower and more stubborn.
How post-inflammatory hyperpigmentation is treated
Marks that can look similar
Post-inflammatory erythema is flat and pink or red, and it fades under pressed glass. It comes from blood vessels, not pigment, so it needs a vascular approach.
You can feel an acne scar as a dip. It is a structural problem and needs structural treatment.
Melasma is symmetrical and driven by sun, heat and hormones, not by an injury. It can sit alongside PIH.
A doctor should rule out acanthosis nigricans, fixed drug eruption, pityriasis versicolor and lichen planus pigmentosus. Each one is handled differently.
Where laser fits
Marks near the surface are managed with the first three stages. Dermal pigment is more likely to need conservative laser. R2 Glow is a non-ablative, long-pulsed 755 nm and 1064 nm system aimed at low-grade inflammation that keeps producing pigment and redness. T2 Frax Radiance is a 785 nm picosecond laser for surface pigment, with a thermal pass aimed at the dermis. Laser toning uses low-fluence 1064 nm. Skin led by redness, and melasma, starts with R2 alone or with no laser at all. Intervals are set at review, not in advance.
Marks on the body
PIH is not only a facial problem. Bites on the legs and arms often leave it. So does eczema in skin folds, rubbing at bra lines, waistbands, inner thighs and underarms, and acne on the back and chest. Shaving, waxing, plucking, burns and grazes can do the same. Before any laser, tell your doctor about every cream, medicine and recent procedure.
Who should wait for laser
Acne, eczema or other irritation in the area should settle first.
Tell your doctor about recent sun exposure and photosensitising medicines. Your doctor will also advise on timing after isotretinoin.
Laser should wait.
A history of keloid scarring needs discussion. Undiagnosed marks need a diagnosis first, as melasma, Hori's naevus and other pigmented lesions can look alike.
Limits and risks
Treatment cannot erase marks on a short timetable. Dermal pigment clears at its own pace, and it can last for years without treatment. Nothing here treats redness or dents, and it will not stop new marks if acne or picking continues. Brief redness and warmth are expected, and treated pigment may look darker before it flakes. Important risks are rebound darkening if energy is too high or sessions are too close, and pale or mottled spots after frequent toning. Blistering or crusting is rare. Risk is higher in darker skin and after sun exposure, so settings stay conservative. Results vary.