The clinical approach
Depth of the pigment sets the ceiling on results
Melanin that stays in the epidermis reads brown and clears comparatively well. Melanin that has dropped into the dermis, taken up by macrophages, reads blue-grey and fights back. Same patient, same trigger, wildly different prognosis. Nothing on a spec sheet changes that, so screen the lesion before anyone sells a package of sessions.
Why 1064 nm keeps showing up
Our engineering archive teaches penetration depth as the distance at which light has attenuated to 37 percent of its entry value, and it's blunt that penetration scales with wavelength. The same material identifies roughly 600 to 1200 nm as the optical window into skin: scattering falls off as wavelength rises, and absorption by the body's own pigments stays limited across that band. 1064 nm sits comfortably inside it. Deep reach, weak grab by epidermal melanin. On Fitzpatrick IV to VI that combination is the entire argument — a shorter, more melanin-hungry wavelength dumps its energy in the exact layer you're trying not to provoke.
532 nm is the other half of the pair, produced by frequency doubling. Shallow, and absorbed hard. Useful on superficial marks in lighter phototypes, risky on dark skin. Two lines on one console, two completely separate risk profiles.
Spot size is a fluence control, not a convenience
Here's where inherited protocols wreck results. Fluence is energy divided by spot area, and area climbs with the square of the diameter. Push 400 mJ through a 2 mm spot and you're near 13 J/cm². Send the identical 400 mJ through a 4 mm spot and it lands closer to 3 J/cm². One click of the regulator, a factor of four. Any settings note that arrives without its spot diameter is worthless to you.
For PIH the direction of travel runs toward the larger spot, the lower fluence, and more passes. Our archive is explicit for patients needing overall tone correction or combined melasma and post-inflammatory pigment: use large-spot Q-switched output on both lines, or expect no clinical result at all. It describes the endpoint as regular mild erythema over the lesion — not frosting, not blistering. It also places general photostimulation-range fluences at roughly 1 to 10 J/cm², energies that usually don't drive a definite temperature rise. That's the neighbourhood a large-spot toning pass actually works in.
Treatment protocol
Control the inflammation before the laser comes out
Our training archive puts this ahead of any device: the key treatment for post-inflammatory hyperpigmentation is controlling the inflammation that caused it. Chase pigment while acne is still flaring and you're refilling the bucket while you empty it. Get the trigger stable, confirm the marks aren't still spreading, then plan a course. Background on the upstream condition sits on our acne and acne scars page.
Confirm it is actually PIH before you fire
PIH takes the shape and area of whatever inflamed the site, and there is a history to match it. A pigmented patch with an irregular border, uneven colour, a recent change in shape or size, or no clear inflammatory history at all is not something to treat as PIH. It goes for biopsy or dermatology referral before a single shot — the rule our QE-01 documentation applies to any lesion you can't confidently identify. Fire first and the histology someone else needs is gone.
Device-level exclusions come off the same manuals: pacemakers and implanted defibrillators, pregnancy, severe diabetes, uncontrolled hypertension, cardiac disease and epilepsy, active herpes or malignant lesions in the field, broken skin, and vascular surgery on the area within the past two months. Keloid-prone patients are a poor fit. Two more questions belong on the intake form — any photosensitising medication, and isotretinoin, which our archive lists on a one-to-two-year look-back among the conditions associated with abnormal wound healing before ablative resurfacing. PIH cases often arrive straight from acne treatment.
Test spot, then titrate
Three to five low-energy shots, watch how the area answers, then commit to a setting. That sequence is written into our device manuals, and it matters more here than in almost any other indication, because the failure mode isn't no result. It's darker than before. On higher phototypes, give the test spot a week or two before you build a whole protocol around it.
Cooling belongs in the parameter set
Operators tend to file cooling under accessories. It isn't. Our archive documents contact cooling with sapphire pre-chilled to 4°C or below, notes that dynamic cryogen cooling runs about twice as efficient as contact cooling, then warns that continuous cryogen spray damages the skin surface and produces post-inflammatory hyperpigmentation in its own right. Spray timing that isn't properly synchronised to the pulse is listed as a serious hazard. Cold air comes off better in that comparison: no consumable, no frostbite, no interference with the beam — though you have to keep the nozzle close and protect ears and nose.
Topicals, timing, and sun
Combination therapy beats any single modality, and the review literature is consistent that treatment should start early, beginning with the inflammatory condition itself, then topical depigmenting agents plus photoprotection. Our archive lists the same tyrosinase-inhibiting family — hydroquinone at 1 to 4 percent, retinoic acid, alpha-hydroxy acids, azelaic acid, kojic acid, glucosamine — and adds a timing note plenty of operators get backwards: in its resurfacing protocols those agents belong after pigment appears, on the order of three to four weeks later, rather than prophylactically before a procedure. Daily broad-spectrum sunscreen isn't optional either. UV undoes the work faster than the laser does it.
Recommended equipment
QN-03 or QE-01: it comes down to spot geometry
Both are Q-switched Nd:YAG platforms running 1064 and 532 nm, and both are legitimate buys. The difference that decides a PIH caseload is how wide you can open the beam.
| Spec | QN-03 | QE-01 |
|---|
| Q-switch type | Passive, chromium-doped crystal | Electro-optic, voltage-driven |
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| Pulse width | 6-8 ns; energy set by pulse count | 6 ns, locked while energy moves |
|---|
| Spot size | 1-4 mm in seven steps | 1-7 mm, continuously adjustable |
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| Single-pulse energy at 1064 nm | 400 mJ (800 / 1200 mJ double / triple pulse) | ≤800 mJ |
|---|
| Fluence at widest spot | About 3.2 J/cm² at 4 mm | About 2.2 J/cm² at 7 mm |
|---|
| Repetition rate | 1-5 Hz | 1-10 Hz |
|---|
| Beam delivery | No articulated arm | 7-joint articulated arm |
|---|
Diffuse post-acne marking across a whole cheek is what the continuously adjustable 1 to 7 mm aperture is for; a handful of well-defined individual lesions is fine on the stepped 2 to 4 mm range.
The QN-03 gives you seven stepped spot sizes from 1 through 4 mm, 6 to 8 ns pulses, 400 mJ single-pulse at 1064 nm, 1 to 5 Hz, water plus air cooling in a 52 kg floor cabinet. It's a passive Q-switch, so turning energy up adds pulses to the train rather than lifting peak power inside one shot.
The QE-01 is electro-optic: 6 ns pulse width that stays locked while you move energy, a 1 to 7 mm continuously adjustable spot, up to 800 mJ (≤800 mJ) at 1064 nm, 1 to 10 Hz. Run 800 mJ through a 7 mm aperture and you land around 2 J/cm² — a genuine large-spot, low-fluence pass with a pulse width you can write down and reproduce visit after visit.
What to keep away from PIH
Ablative resurfacing, mainly. Our archive is unambiguous that ultrapulse CO2 carries the highest pigment-change rate among the resurfacing modalities it compares, with modulated Er:YAG in the middle and short-pulse Er:YAG lowest, and it singles out Fitzpatrick IV and above as a group where post-CO2 pigmentation is close to routine. That doesn't make the CF-01 a bad machine. It makes it the wrong machine for this job. The same logic rules out millisecond hair and vascular platforms, which heat tissue instead of fracturing particles. For superficial post-acne marking on lighter phototypes an E-light platform like the MF-05 earns its place, though our parameter charts stop at type V for the IPL modes and the safety margin narrows fast as skin darkens. Cases that overlap with melasma want the same low-and-slow discipline, only more of it.
Acceptance, safety and the paperwork
These are Class 4 laser products. The applicable particular standard is IEC 60601-2-22, currently in its 2019 fourth edition, covering basic safety and essential performance for surgical, cosmetic, therapeutic and diagnostic laser equipment. Ask for the test report, not just a mark on the carton. Wavelength-rated eyewear for operator and patient is mandatory — our archive records retinal injury as a live risk with both intense light and laser sources. Check your national route as well: in the US these sit under the FDA as regulated medical devices, and cleared indication language is narrower than marketing language almost every time. Install notes and consumables live on our service page, and if you want a parameter sheet built around a specific caseload, talk to us.
Frequently asked questions
Can a laser clear PIH completely?
Sometimes. Nobody should promise it. Epidermal pigment responds well; dermal pigment, the blue-grey kind, is slow and may never fully resolve, and StatPearls says as much. Energy-based work mostly shortens a process that would otherwise run six to twelve months on its own for epidermal cases, and it performs best alongside topicals and strict sun protection rather than instead of them.
Which spot size should I start with on Fitzpatrick V or VI?
The largest one that still gives you a visible endpoint, which in practice means the widest aperture on the handpiece and 1064 nm only. Work out fluence before you fire: energy divided by spot area, every single time. Then test spot, wait, judge. Higher phototypes are exactly the population where an aggressive setting produces more pigment instead of less, and that's the whole reason a continuously adjustable spot earns its price difference.
How many sessions, and how far apart?
Several, spaced weeks apart, and be sceptical of anyone quoting an exact number sight unseen. Fragmented pigment leaves through phagocytosis and lymphatic drainage, which takes time, so tightening the interval speeds up nothing. It just stacks thermal insult. Dermal pigment runs longer than epidermal. Depth, phototype and how well the patient stays out of the sun move the count far more than the machine does.
Is my cooling system itself a risk factor?
It can be. Cryogen spray held on too long is documented in our archive as a cause of post-inflammatory hyperpigmentation, and desynchronised spray timing is worse than that. Contact cooling needs the sapphire genuinely down at 4°C or below with full skin contact before the pulse fires. Cold air sidesteps both failure modes, at the cost of a compressor running in the treatment room. Whichever you buy, commission it and check it periodically — a cooling fault announces itself as pigment, not as an error code.
Do I need a separate machine for the acne and for the marks it left?
Usually, yes. Active inflammatory acne answers to filtered light and mechanical pore clearance. Residual pigment needs nanosecond photoacoustic work. Clinics with a heavy post-acne caseload commonly run an E-light platform for the active phase and a Q-switched Nd:YAG for what it leaves behind. Our full product range is the place to start if you're building the room from scratch.
References
- Davis EC, Callender VD. Postinflammatory hyperpigmentation: a review of the epidemiology, clinical features, and treatment options in skin of color. J Clin Aesthet Dermatol. 2010;3(7):20-31.
- Postinflammatory Hyperpigmentation - StatPearls, NCBI Bookshelf (National Library of Medicine).
- IEC 60601-2-22:2019 - Medical electrical equipment, Part 2-22: Particular requirements for basic safety and essential performance of surgical, cosmetic, therapeutic and diagnostic laser equipment.
- U.S. Food and Drug Administration - Medical Lasers (Center for Devices and Radiological Health).