Key facts
- What PIH is
- Melanin left in the epidermis or dropped into the dermis after acne, eczema, injury, friction or a treatment
- Confirmed by
- History of a preceding injury, distribution, and examination under appropriate light to judge depth
- Pico's role
- Low-energy toning for marks that persist after the cause is controlled; not a first step
- Settings logic
- Longer wavelength, low fluence, long intervals, test area in darker skin, stop if darker
- The paradox
- The same laser that clears PIH can cause it if energy, interval or sun exposure is wrong
- Fee
- Set in writing after assessment; see how fees are quoted
How is PIH confirmed, and how deep does the pigment sit?
Post-inflammatory hyperpigmentation is confirmed by its history: a mark in the shape of something that happened there before. Before pico laser is discussed, Dr Sin Yong asks what preceded the mark, whether acne, eczema, an insect bite, a burn, friction, a chemical peel or a previous laser, and whether that cause is still active. The post-inflammatory hyperpigmentation page describes the condition; this page covers only the picosecond laser's place in managing it.
Depth decides how the mark behaves. Pigment that sits in the epidermis looks brown, has a defined edge and tends to clear faster; pigment that has dropped into the dermis looks grey or slate-blue, has a softer edge and clears slowly or incompletely. Examination under appropriate light helps judge which applies, and a pink or red mark is separated out as post-inflammatory erythema, which is vessels rather than pigment and is not a picosecond target. Melasma, which can be mistaken for PIH on the cheeks, is also ruled out, because it is managed differently.
What does pico laser do for PIH, and why is it not the first step?
Pico laser fragments the melanin that inflammation has left behind so that the skin clears it faster than it otherwise would. The picosecond pulse does this mainly by a pressure effect, with less heat spreading into the surrounding skin than a longer pulse produces, which matters in a mark that exists because the skin over-responds to injury. It is delivered as low-energy toning across the mark rather than as the higher-energy spot treatment used for a sun spot.
It is not the first step because PIH fades on its own once its cause has stopped, and because every laser pass is itself an injury. Controlling the acne or eczema, stopping the friction, protecting the skin from the sun and allowing time clears many marks without any device. Toning is considered for marks that are persisting after the cause is controlled, that trouble the person and whose depth suggests they will respond. The acne treatment page covers how the commonest cause is brought under control.
“Pigment already deposited is a deposit. Inflammation is what keeps producing it.”
Dr Sin YongOn treating upstream or downstream
How are the settings chosen when the skin is already prone to darkening?
Settings for PIH are chosen on the assumption that the skin will over-react, because it already has once. A longer wavelength that epidermal melanin absorbs less strongly, a low fluence, a larger spot and long intervals between treatments all reduce the heat and inflammation delivered to the surrounding skin. In Fitzpatrick IV and V skin a small test area is often treated first, and the response at review decides whether the plan continues or stops.
A stop rule is part of the plan. A mark that darkens after a treatment is reviewed and rested rather than treated again, and toning is not repeated on a standing schedule, because frequent repeated toning of the same area has been linked to pale mottled spots. A recent tan, active inflammation in the area, photosensitising medication and recent isotretinoin are each reasons to defer. The article on pico laser on Asian skin explains why these variables matter more than the device name.
Can pico laser cause PIH, and what are the other risks?
Yes. The same laser that clears a post-inflammatory mark can create one, because the mark is the skin's response to injury and a laser is an injury. Energy too high for the skin, passes stacked over the same area, treatment repeated before the skin has settled, sun on freshly treated skin and treating over active inflammation are the usual causes. The darkening that follows tends to fade with time and protection, but it can take a long time, which is why prevention carries more weight than correction.
The other risks are those of any toning plan: pale or mottled spots from frequent repetition, transient redness and warmth, and uncommonly blistering or pinpoint bleeding at higher energies. Picking at any fine crust, scrubbing the area or restarting exfoliating acids too soon each add inflammation. New darkening weeks after treatment should be reviewed rather than treated over, and the complication care page lists the signs that need same-day attention.
What is combined with pico laser, and what determines the fee?
Treating the cause is combined with every PIH plan, because a mark that keeps being made cannot be cleared. Acne is brought under control, eczema is settled, friction from masks, straps or rubbing is identified and stopped, and squeezing is discouraged, because each new episode of inflammation places another deposit. Daily broad-spectrum sun protection follows, since ultraviolet exposure deepens a fresh mark and slows its clearance.
Topical therapy is the next layer, and it is a doctor's decision rather than a shelf purchase. Prescription agents that slow pigment production or speed cell turnover, such as hydroquinone, tretinoin or azelaic acid, each have side effects and are chosen after assessing the skin and the cause. The fee for a plan that includes toning depends on the area, the depth and extent of the marks, whether a test area is treated first and how the plan is staged; Singapore's rules prevent prices from being advertised, and a written quote follows assessment, as the how fees are quoted page explains.
