Different types of acne scars need different treatments, and using the wrong laser or filler on the wrong scar wastes both time and money. Ice pick, boxcar, and rolling scars each sit at a different depth and structure, which is why a proper dermatology assessment matters more than any single device. This blog will walk you through how to identify each scar type and which treatments actually work for each.
Why Scar Type Dictates the Entire Treatment Plan
Roughly 80 to 90 percent of acne scars are atrophic, meaning they form when healing produces less collagen than the original tissue lost. The remaining percentage are hypertrophic or keloid, raised scars caused by excess collagen. The atrophic group is where most confusion happens, because the three main subtypes look broadly similar under poor lighting but respond to completely different procedures.
A scar that looks like a small pit might be an ice pick, which reaches deep into the dermis, or a shallow boxcar, which sits close to the surface. Treating the first with a resurfacing laser and the second with subcision produces minimal change in either case. The tool has to match the anatomy.
How acne becomes a scar in the first place
A scar begins when inflammation from acne reaches the dermis, the structural layer where collagen lives. Deep lesions such as nodules and cysts cause the most damage. When the lesion resolves, the body rebuilds the area with collagen, but the rebuilding is often imperfect. Too little collagen produces an indentation. Too much produces a raised lump. The exact depth, shape, and tethering of the resulting scar depend on how far down the original inflammation reached and how each person’s tissue heals.
This is why early and proper medical treatment of active acne is the single most effective form of scar prevention. Once a scar has formed, it becomes a structural problem, not an inflammatory one, and the treatment logic changes entirely.
The Three Main Types of Atrophic Acne Scars
Ice pick scars
Ice pick scars are narrow, deep punctures less than 2mm wide that extend vertically into the deep dermis or subcutaneous tissue. They have a V-shaped cross-section and sharp margins, resembling a small hole made by a sharp instrument. According to a peer-reviewed review of acne scar pathogenesis, ice pick scars account for 60 to 70 percent of atrophic acne scars and are the most resistant to conventional resurfacing.
They usually appear on the forehead, upper cheeks, and temples, where the skin is thinner. Depth is the problem. A fractional CO2 laser works at the surface and upper dermis, but cannot reach the base of a true ice pick scar. Treatment needs to reconstruct the scar from the bottom up.
The two most effective options are TCA CROSS, which involves applying high-concentration trichloroacetic acid into the scar base to stimulate focal collagen production, and punch excision, which surgically removes the scar and closes the defect. Fractional CO2 laser is added afterwards to smooth the surrounding surface once the deeper reconstruction has taken.
Boxcar scars
Boxcar scars are broader, oval or rectangular depressions with well-defined vertical edges. They typically measure 1.5 to 4mm in width and 0.1 to 0.5mm in depth, giving them a U-shape or the look of a small crater. Many patients describe them as resembling chicken pox scars.
Because the depth is shallower and the floor of the scar is flat rather than tapered, boxcar scars respond well to resurfacing. Fractional CO2 laser is generally the first-line choice for shallow boxcar scars, as the ablative microzones stimulate collagen remodelling across the scar base and blend the edges with the surrounding skin. Deeper boxcar scars often need punch elevation, where the base is surgically lifted to the surrounding skin level, followed by laser to refine the edges. Radiofrequency microneedling is a useful alternative in patients with darker skin types, where aggressive ablative lasers carry a higher pigmentation risk.
Rolling scars
Rolling scars are broad depressions with soft, sloping edges that create a wavy, uneven appearance across the skin. They are most common on the lower cheeks and jawline, where the skin is thicker, and are rarely deep but can cover a wide area.
The mechanism is different from ice pick and boxcar. Rolling scars are caused by fibrous bands tethering the dermis to deeper subcutaneous tissue. The surface looks pulled down because it literally is. A laser that resurfaces the top of this scar will produce almost no change, because the tether underneath is still pulling the skin down.
Subcision is the first-line treatment. A specialised needle or blunt cannula is inserted under the scar to sever the fibrous bands, releasing the tether and allowing the skin to rise. New collagen forms in the released space during healing. For stubborn rolling scars, a second subcision session or the addition of a dermal filler such as hyaluronic acid or poly-L-lactic acid can hold the skin elevated long enough for lasting collagen remodelling. Lasers or RF microneedling are then layered on top to refine the surface. Attempting to treat rolling scars with resurfacing alone is the most common reason patients come to a clinic after months of laser sessions reporting no meaningful change.
Most Patients Have More Than One Scar Type
Clinical practice rarely involves a single scar type in isolation. A patient with a history of moderate to severe inflammatory acne typically presents with a mix: ice pick scars on the cheeks, a few boxcar scars along the jaw, and rolling scars across the mid-face. Scar counts, depths, and patterns also vary between the left and right sides of the face based on sleeping habits and sun exposure.
The practical consequence is that any credible acne scar revision plan will combine procedures, sequenced across multiple sessions rather than delivered in one visit. A typical protocol might look like subcision for rolling scars at session one, TCA CROSS for ice pick scars at session two, fractional CO2 laser at session three, then a pigment or vascular laser at the end to clear residual marks. Each session is spaced four to eight weeks apart to allow proper collagen remodelling between treatments.
Telling true scars from post-acne marks
Not every discolouration left after acne is a scar. Post-inflammatory erythema appears as flat red or pink marks, caused by dilated capillaries under the skin. These respond to pulsed dye or vascular lasers, not to resurfacing. Post-inflammatory hyperpigmentation appears as flat brown marks, common in Asian and darker skin types, and responds to topical tyrosinase inhibitors, chemical peels, and pigment-targeting lasers such as picosecond devices.
True scars involve textural change. If you run a finger over the area and feel an indentation, it is a scar. If the skin is smooth but discoloured, it is a mark. Marks generally fade within six to eighteen months even without treatment. Textural scars do not fade. Mistaking one for the other leads patients to spend on the wrong procedure.
Hypertrophic and keloid scars sit in a different category
Raised acne scars, typically on the jawline, chest, or shoulders, are driven by excess collagen rather than loss. These need intralesional corticosteroid injections to soften the tissue and pulsed dye laser to reduce redness and volume over time. Aggressive resurfacing lasers are generally avoided, as they can worsen keloidal tissue.
What a Specialist Scar Assessment Actually Involves
Proper lighting and palpation
Scar assessment cannot be done under flat overhead lighting. Oblique side-lighting reveals depth and shadow patterns that flat light hides, and standardised clinical photography helps track response across sessions. A finger test against the scar also matters. Pressing a rolling scar while stretching the surrounding skin often flattens it, because stretching temporarily releases the tether. An ice pick scar does not flatten under stretch, because the anatomy is a deep vertical tract, not a tether.
Matching tool to tissue
A specialist assessment at a dermatology consultation results in a mapped plan, not a single generic package. Expect a list of scar types identified, a matched sequence of procedures, and a realistic estimate of sessions required. Most patients see 50 to 70 percent improvement in scar appearance across a complete protocol. Total clearance is uncommon for deep or long-standing scars, and any clinic promising otherwise should be treated with caution.
The Dermatological Society of Singapore’s clinical guidance on acne and post-acne management reinforces this point, noting that combined modality approaches consistently outperform single-device protocols and that early referral for persistent or scarring acne reduces long-term scar burden.
Singapore-Specific Considerations
Darker Fitzpatrick skin types, which dominate the local patient mix, respond differently from lighter skin to aggressive ablative treatments. The risk of post-inflammatory hyperpigmentation after fractional CO2 laser is real and must be managed with pre-treatment pigmentation protocols, conservative energy settings, and strict post-procedure sun protection. Picosecond lasers and radiofrequency microneedling are often safer choices for patients with a history of easy pigmentation.
Practical expectations also shift in the tropical climate. Downtime after ablative resurfacing requires careful planning. Raw skin reacts poorly to humidity and sweat, and sun exposure in the weeks following treatment must be minimised to prevent hyperpigmentation on the treated area. A clinic with experience in laser acne scar treatment calibrated for Singapore skin types will schedule sessions accordingly, usually avoiding major outdoor seasons or vacation windows for the first week post-procedure.
Conclusion
Ice pick, boxcar, and rolling scars look similar at a glance but sit at different depths, with different anatomy, and respond to different procedures. Subcision releases tethers. TCA CROSS rebuilds narrow tracts. Fractional CO2 resurfaces shallow craters. Most real treatment plans combine all three across several sessions, calibrated for each patient’s skin type and scar mix.
Book a scar assessment with Dr Ang Sue-May at Skincodes to get your scars mapped and a treatment sequence planned before spending on another generic laser package.
FAQs About Types of Acne Scars
How do I tell if my acne scar is ice pick, boxcar, or rolling?
Ice pick scars are narrow (under 2mm), deep, and V-shaped. Boxcar scars are broader with sharp, vertical edges and a flat base. Rolling scars are wide with sloping edges and a wavy surface. A dermatologist uses side-lighting and a stretch test to confirm, since most patients have a mix.
Which type of acne scar is hardest to treat?
Ice pick scars are the most treatment-resistant because their depth reaches beyond what fractional CO2 laser can reshape. TCA CROSS and punch excision work best for ice pick scars, usually across multiple sessions, followed by laser resurfacing to smooth the surrounding skin.
Is subcision effective for all acne scars?
No. Subcision works specifically for tethered rolling scars, where fibrous bands pull the skin downward. It is not effective for ice pick scars and offers limited benefit for shallow boxcar scars. Using subcision on the wrong scar type is a common reason patients see minimal improvement.
How many sessions of laser acne scar treatment are usually needed?
Most patients in Singapore need three to six sessions spaced four to eight weeks apart, often combining fractional CO2 laser with subcision, TCA CROSS, or RF microneedling. Expected improvement is around 50 to 70 percent across a full protocol, depending on scar depth, skin type, and patient healing response.
Can acne scars be treated while acne is still active?
Scar revision works best once active acne is controlled, because ongoing inflammation produces new scars during healing. A dermatologist will usually stabilise acne first with prescription treatment, then plan scar procedures once the skin has been clear for several months.
The information in this article is general and educational. It does not replace a personal consultation, diagnosis, or treatment from a qualified doctor. Please seek advice from a doctor about your individual skin condition.