The Science of Acne Scars — Why They Form and How to Treat Each Type
True acne scars are structural damage to the dermis, not surface stains — understanding the four scar types and the collagen-rebuilding treatments matched to each one is the foundation of any realistic improvement plan.
Key Takeaways
- True acne scars are dermal structural injuries caused by inflammatory breakdown of collagen, which is why no surface-applied cream can reverse them.
- Each scar subtype requires a matched treatment: TCA CROSS for ice pick scars, RF microneedling or fractional laser for boxcar scars, and subcision combined with RF microneedling for rolling scars.
- Post-inflammatory redness (PIE) and brown marks (PIH) are not true scars and respond to vascular or pigment-targeting lasers plus strict sun protection rather than collagen-remodelling procedures.
- Realistic improvement for atrophic acne scars is typically 50 to 80 percent over 6 to 12 months with a correctly sequenced, multi-session treatment plan.
- Dr. Dan Xu, MD, CCFP at ID Cosmetic Clinic in Markham performs in-person scar morphology assessments to build individualized protocols, because accurate classification is the foundation of effective treatment.
Direct Answer
Acne scars are areas of permanent dermal structural damage caused when intense follicular inflammation destroys collagen and elastin fibres in the deeper layers of the skin; because the injury is below the epidermis, topical products cannot rebuild the collapsed collagen framework, and effective treatment must stimulate controlled collagen remodelling from within the dermis. Clinicians classify true acne scars into three atrophic subtypes — ice pick, boxcar, and rolling — plus post-inflammatory pigment changes (PIE and PIH) that are often mistakenly grouped with them but respond to entirely different interventions. Ice pick scars are deep, narrow channels that respond well to TCA CROSS, a technique that deposits concentrated acid at the base of the track to trigger focal collagen repair. Boxcar scars have sharply defined edges and shallow-to-moderate depth, making them good candidates for radiofrequency microneedling and fractional laser resurfacing. Rolling scars result from fibrous tethering of the dermis to underlying tissue, so subcision — a procedure that physically releases those adhesions — is typically combined with RF microneedling to lift and remodel the surface simultaneously. Post-inflammatory erythema (the pink-red marks) and post-inflammatory hyperpigmentation (the brown marks) are vascular and pigmentary changes in living tissue, not true scars; targeted laser therapy and consistent broad-spectrum sun protection are the appropriate approach. Realistic outcomes across all true scar types generally range from 50 to 80 percent improvement over 6 to 12 months with a properly sequenced treatment plan, and most patients require a series of sessions rather than a single procedure. At ID Cosmetic Clinic in Markham, Dr. Dan Xu, MD, CCFP — a CPSO-licensed physician and the clinic's founder and medical director — conducts in-person assessments to classify each patient's scar morphology before recommending a protocol, because matching the correct modality to the correct scar type is the single most important variable in achieving meaningful results.
Quick answer: True acne scars are not surface stains that “fade with time” — they are structural damage to the deeper dermis, so the goal of acne scar treatment is to rebuild collagen, not bleach a mark. There are four things people call “acne scars,” and each needs a different approach: ice pick scars (deep, narrow — best treated with TCA CROSS), boxcar scars (sharp-edged craters — RF microneedling and fractional laser), rolling scars (wavy tethering — subcision plus RF microneedling), and pigment marks (PIE redness and PIH brown marks — which are not true scars and often improve with the right laser plus strict sun protection). Realistic improvement is usually 50–80% over 6–12 months, not 100% erasure.
Medically reviewed by Dr. Dan Xu, M.D., CCFP — CPSO Licensed Physician and Founder & Medical Director of ID Cosmetic Clinic, Markham. Last updated June 2026.
“Why won’t my acne scars just go away?” is one of the most common questions we hear in our Markham clinic — often from patients who have spent years and a lot of money on serums that were never going to work. The honest answer is rooted in skin biology: most over-the-counter “scar” products target the surface, while the scar that actually changes how your skin catches the light lives much deeper. This guide explains the science of how acne scars form, how to identify which type you have, and the treatment that genuinely matches each one. It is general information, not medical advice — your own plan should come from an in-person assessment.
Acne scars are not a surface problem: a quick lesson in skin biology
Your skin has three layers. The epidermis is the thin outer barrier. Beneath it sits the dermis — the structural scaffold, rich in collagen and elastic fibres, that gives skin its bounce and smoothness. Below that is subcutaneous fat. When an acne lesion is inflamed deeply and intensely enough, the inflammation damages the collagen architecture of the dermis. How the body repairs that damage decides whether you end up with a scar — and what kind.
This is the key point most product marketing ignores: a true acne scar is dermal structural damage. No cream, no matter how expensive, can rebuild a collapsed collagen framework from the surface. That is why effective acne scar treatment is, at heart, a process of controlled collagen remodelling — and why a one-size-fits-all “scar treatment” so often disappoints.
How acne scars form: inflammation and dermal damage
Acne is a chronic inflammatory disease of the hair-follicle–oil-gland unit. When a pore clogs and Cutibacterium acnes bacteria multiply, the immune system mounts an inflammatory response. That response releases enzymes and inflammatory mediators that kill bacteria — but in the crossfire they also break down surrounding collagen and elastin. Several factors then decide whether a scar forms:
- How deep the inflammation went. Surface blackheads and whiteheads rarely scar. Deep cystic and nodular acne can damage the full thickness of the dermis. The deeper and longer the inflammation, the higher the scar risk.
- Which way healing went wrong. If the dermis under-produces collagen during repair, the skin can’t fill the defect and you get an atrophic (depressed) scar. If it over-produces collagen in a disorganised pile, you get a hypertrophic or keloid (raised) scar.
- Your genetics and skin type. Two people with identical cystic acne can heal completely differently. Asian and other deeper skin types tend toward over-repair, so raised scars, keloids and post-inflammatory pigment are relatively more common — a pattern that matters here, because our practice primarily serves Asian faces.
- How quickly the acne was treated. Early, proper acne control (topical retinoids, oral antibiotics, or isotretinoin when indicated) shortens inflammation and measurably lowers the chance of scarring.
Why you must never squeeze a pimple
Picking or squeezing pushes inflammation outward through the follicle wall, driving bacteria and inflammatory debris into the surrounding dermis and enlarging a once-contained lesion several-fold. That is the real mechanism behind “every time I pop one, it scars” — you are manually expanding the zone of dermal injury. If a lesion truly needs draining, it should be done by a clinician under sterile conditions, not over a bathroom sink.
The 4 types of acne scars: which one do you have?
Correctly identifying your scar type is the whole game — it dictates the treatment. Clinicians often use oblique (side) lighting to read the depth, edges and texture of a scar more clearly than flat front-on light allows. Here are the four categories, including the two “pseudo-scars” that are really pigment, not structural damage.
1. Ice pick scars
The easiest type to recognise: deep, narrow, V-shaped pits with a small surface opening that taper down into the deep dermis — like a puncture left by an ice pick. They are the hardest type to treat because their depth often exceeds the working range of standard lasers and microneedling, which act on the upper-to-mid dermis and simply cannot reach the bottom of the pit. The most effective starting treatment is TCA CROSS (Chemical Reconstruction of Skin Scars), in which a high-concentration trichloroacetic acid is precisely dotted into the base of each scar to trigger controlled local injury and fresh collagen formation, gradually lifting the floor of the pit.
2. Boxcar scars
Wide depressions with sharp, well-defined vertical edges — round or oval, like marks from a hole punch, shallow to moderate in depth. Because their shape is relatively regular and their walls are reachable, boxcar scars respond well to RF microneedling and fractional laser, which stimulate new collagen to fill the depression and soften the abrupt edges.
3. Rolling scars
Soft, wavy, undulating depressions — broad and relatively shallow, giving the skin a gently rolling, hilly look. Their cause is different from the others: fibrous bands beneath the skin (formed during acne healing) tether the dermis down to the deeper tissue, pulling the surface into a dip like guy-ropes. This means treating rolling scars isn’t only about building collagen — you often also need to release the tethering bands with a technique called subcision, so the skin can actually rebound rather than just thicken on top. Subcision combined with RF microneedling tends to work best here.
4. Pigment changes: PIE and PIH (not technically “scars”)
Many people lump red and brown post-acne marks in with “scars,” but biologically these are post-inflammatory pigment changes with no structural dermal damage — which means they can fade on their own, though it may take 6–24 months and they darken with sun exposure.
PIE (post-inflammatory erythema): red or pink marks caused by residual dilated blood vessels. During inflammation the skin grows extra vessels to speed healing; when some fail to fully regress, you see red marks. Vascular-targeting modes on certain RF microneedling platforms (such as the pulsed-wave mode on Sylfirm X) can selectively address these abnormal vessels.
PIH (post-inflammatory hyperpigmentation): brown or dark marks from inflammation driving melanocytes into overdrive and depositing melanin. The deeper your skin tone (Fitzpatrick IV–VI), the higher the PIH risk and the slower it clears. Picosecond (pico) lasers paired with brightening actives (niacinamide, arbutin, vitamin C) are the mainstream approach — but strict daily sun protection is the non-negotiable foundation, because any UV exposure re-stimulates pigment and dramatically lengthens recovery.
The best treatment for each acne scar type
There is no universal acne scar treatment. A physician builds a staged, individualised plan based on scar type, depth, skin tone and overall skin health. The table below summarises the evidence-based pairing of scar type to treatment; the sections that follow add the practical detail.
| Scar type | What it looks like | First-line treatment | Typical course* |
|---|---|---|---|
| Ice pick | Deep, narrow pits | TCA CROSS (then RF microneedling for texture) | ~4–6 sessions, 6–8 wks apart |
| Boxcar | Wide craters, sharp edges | RF microneedling + fractional laser | RF ×3–4, then laser ×1–2 over 6–12 mo |
| Rolling | Wavy, tethered dips | Subcision + RF microneedling | Subcision ± RF ×3–4 over 6–12 mo |
| PIE (red marks) | Flat red/pink marks | Vascular-mode RF microneedling + sun protection | Series of sessions; sunscreen ongoing |
| PIH (brown marks) | Flat brown/dark marks | Pico laser + brightening actives + sun protection | Series of sessions; sunscreen ongoing |
*General ranges only — your actual protocol depends on your assessment. Note on devices: “RF microneedling” and “fractional laser” describe treatment categories. ID Cosmetic Clinic uses comparable medical-grade platforms (for RF microneedling, devices such as Lutronic Genius and Sylfirm X). This is not a claim about any one branded system being right for you.
Ice pick: TCA CROSS first, RF microneedling second
High-concentration TCA is dotted precisely into the floor of each pit, inducing a controlled, localised injury that the skin repairs with fresh collagen — slowly raising the deep base. Treatment usually takes several sessions spaced 6–8 weeks apart. Early on, a scar may briefly look deeper as crusts form and shed; this is a normal part of the process. Once the floor of the ice pick has lifted, RF microneedling (e.g. Lutronic Genius) can refine the edges and overall texture. Using RF microneedling alone on true ice pick scars tends to under-deliver — depth is the reason.
Boxcar + rolling: RF microneedling, fractional laser, and subcision in stages
RF microneedling devices such as Lutronic Genius and Sylfirm X drive fine needles into the dermis and deliver radiofrequency energy at depth, heating the dermis precisely to stimulate collagen remodelling. A real advantage for our patient base: RF microneedling is far less dependent on skin colour than older lasers, so it is generally safer in deeper skin tones with a lower risk of triggering PIH.
For rolling scars, subcision is often done before or alongside RF microneedling — a fine needle is fanned beneath the scar to release the fibrous bands tethering the skin down, so the surface can lift back into place rather than stay pulled. Fractional laser resurfacing (e.g. an ablative fractional CO₂ platform such as eCO2 Plus) creates uniform micro-columns of controlled injury to drive epidermal renewal and deeper collagen rebuilding; it is particularly good at smoothing the sharp edges of boxcar scars and is usually alternated with RF microneedling rather than stacked on the same day. A typical full cycle might be RF microneedling ×3–4 (every 4–6 weeks) plus fractional laser ×1–2, over roughly 6–12 months.
PIE (red marks): vascular-mode treatment + strict sun protection
Sylfirm X is one of the few RF microneedling platforms with both continuous-wave and pulsed-wave modes; the pulsed-wave mode can selectively target the abnormal new blood vessels behind PIE. Diligent sun protection (SPF 50+, reapplied) afterwards is required to hold the result.
PIH (brown marks): pico laser + brightening actives + strict sun protection
Picosecond lasers (such as PicoSure or PicoWay) use ultra-short pulses to shatter melanin particles; combined with daily brightening actives (niacinamide, arbutin, vitamin C) they can speed PIH clearance. But the single most important factor is sun protection — any lapse can partially reverse hard-won progress.
An honest note on expectations
For atrophic scars — especially ice pick and deep boxcar — the realistic goal is significant improvement, not 100% erasure. Once the dermal architecture is damaged, a complete return to never-injured skin is essentially impossible. But with a systematic, staged plan, most patients can reach roughly 50–80% (sometimes more) improvement, so the scars are no longer obvious in normal light. This takes 6–12 months of consistent treatment and patience; it is not a one-session fix, and anyone promising otherwise is overselling. A representative before-and-after from our own patients can be shown at consultation
Who should be cautious with acne scar treatment?
Energy-based scar treatments are widely suitable but not for everyone. You should postpone or get specialised assessment first if you have active, inflamed acne (it is usually best to settle the acne before resurfacing scars), an active skin infection or cold sore in the area, a history of keloids (aggressive resurfacing can provoke them — a conservative, test-spot approach is wise), or if you are pregnant or breastfeeding. Recent isotretinoin use, certain photosensitising medications, and a tendency to PIH in deeper skin tones all change the plan — which is exactly why device choice and settings should be individualised by a physician. This article is general information, not medical advice.
The best treatment is prevention: don’t pick, and intervene early
From a dermatological standpoint, the most effective “treatment” for acne scars is preventing them. Once the dermis is damaged, every later treatment — however advanced — is essentially damage control.
- Treat acne early and properly. Moderate-to-severe acne (especially cystic and nodular) is not something to “wait out.” Each flare adds dermal injury. Early systematic treatment — topicals, oral antibiotics, and isotretinoin when indicated — meaningfully lowers both the rate and severity of scarring.
- Never squeeze your own pimples. However “ready” a lesion looks, self-squeezing spreads bacteria into the surrounding dermis and deepens the injury. Let a clinician handle anything that needs draining.
- Use sun protection to limit PIH. UV keeps melanocytes active, making brown marks darker and slower to clear. Daily SPF 50+, midday shade and physical cover are the lowest-cost, highest-return habit for post-acne marks.
- If a scar has formed, treat it sooner rather than later. Intervening within the first 6–12 months generally outperforms treating old scars, because dermal remodelling is still active and more responsive. Atrophic scars do not disappear on their own — “waiting to see” usually just misses the best window.
Frequently asked questions
What is the best treatment for acne scars?
There isn’t one best treatment — it depends on the type. Ice pick scars respond best to TCA CROSS; boxcar scars to RF microneedling and fractional laser; rolling scars to subcision plus RF microneedling; and red or brown marks (PIE/PIH) to vascular-mode treatment or pico laser plus strict sun protection. A correct diagnosis of your scar type is the most important step.
Can old acne scars still be treated, or is it too late?
Old scars can still be treated, but improvement is usually less than for newer ones. Scars within about 6–12 months remodel more readily. Older scars have heavily fibrosed collagen and often need more sessions and stronger combinations (for example TCA CROSS plus RF microneedling). Age of the scar doesn’t make it untreatable — it just calls for a fuller plan and patience.
What’s the difference between PIE and PIH?
PIE (post-inflammatory erythema) is a flat red or pink mark from leftover dilated blood vessels. PIH (post-inflammatory hyperpigmentation) is a flat brown or dark mark from excess melanin. Neither is a true structural scar, both can fade over time, and both improve faster with strict sun protection — but they need different treatments because one is vascular and the other is pigment.
How many sessions will I need to treat acne scars?
It varies by type and severity. A common atrophic-scar cycle is around 3–4 RF microneedling sessions plus 1–2 fractional laser sessions over 6–12 months; ice pick scars often need 4–6 TCA CROSS sessions spaced 6–8 weeks apart. Your exact course is set after an in-person assessment.
Can I treat acne scars while I still have active acne?
Ideally you settle the active acne first, then treat the scars — otherwise you may be forming new scars while resurfacing old ones, which is inefficient. If a new pimple appears mid-course it can usually be managed between sessions without derailing the overall plan. Your physician will sequence the timing.
Will RF microneedling or laser cause pigmentation in darker or Asian skin?
Any energy treatment carries some PIH risk in deeper skin tones, which is precisely why device choice and settings matter. RF microneedling is generally safer than older ablative lasers for darker and Asian skin because it is less dependent on skin colour, and conservative settings with diligent post-care and sun protection further lower the risk.
Can I treat acne scars at home with a dermaroller?
It’s not recommended. Home dermarollers are usually ≤0.5 mm — too short to reach the dermis and rebuild collagen — and improper hygiene risks infection. Rolling over active acne can also spread bacteria and worsen scarring. Medical RF microneedling reaches far deeper (up to ~3.5 mm) with precise radiofrequency energy; it is a fundamentally different treatment. Home devices are better thought of as skincare-absorption aids, not scar treatments.
Do acne scars ever go away on their own?
True atrophic scars (ice pick, boxcar, rolling) do not — they are structural dermal damage and will not self-resolve. Pigment marks (PIE and PIH) are different: they often fade on their own over many months, especially with good sun protection, though treatment can speed that up.
How much does acne scar treatment cost in Markham?
Cost depends on the scar type, the number of sessions, and the combination of treatments used. Because plans are individualised, we quote after assessing your skin in person. As a guide, expect pricing in the range of Quoted at consultation per session for RF microneedling and Quoted at consultation for a TCA CROSS or fractional laser session; your full plan is estimated at consultation.
Related at ID Cosmetic Clinic
- Treatment: RF Microneedling (Lutronic Genius / Sylfirm X)
- Treatment: Fractional Laser Resurfacing
- Treatment: Pico Laser for Pigment
- Condition: Acne Scars · Acne
- Compare: RF Microneedling vs Laser for Scars
- Read next: PIE vs PIH: Red Marks vs Brown Marks After Acne
Not sure which type of acne scar you have? Book a consultation at ID Cosmetic Clinic in Markham — Dr. Dan Xu will assess your scars under proper lighting and give you a staged, honest treatment plan matched to your skin.
📍 30 Gibson Dr, Units 113-117, Markham, ON L3R 2S3 · 📞 905-477-2225 · ✉️ [email protected] · 🕒 Mon–Sun 10:00–18:00
Frequently Asked Questions
Frequently Asked Questions
What is the best treatment for acne scars?
Can old acne scars still be treated, or is it too late?
What is the difference between PIE and PIH?
How many sessions will I need to treat acne scars?
Can I treat acne scars while I still have active acne?
Will RF microneedling or laser cause pigmentation in darker or Asian skin?
Can I treat acne scars at home with a dermaroller?
Do acne scars ever go away on their own?
How much does acne scar treatment cost in Markham?
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