Guide · Boxcar acne scars
Boxcar scars treatment in Singapore: shallow or deep, which methods fit, and what improvement is realistic
Boxcar scars are the round, sharp-edged dips that acne can leave behind, and they rarely respond to one machine on its own. Here is how shallow and deep boxcar scars differ, which treatments match each, why a combined plan usually works better, how long it takes, and how the risk of dark marks in Asian skin is kept down.
Written & medically reviewed by Dr Sin Yong · 9 October 2026
Quick answer
- Boxcar scars are round or oval depressed acne scars with sharp, vertical edges and a flat floor, usually about 1.5 to 4 mm wide. They are one of three atrophic scar types, alongside rolling and ice pick scars, and many faces have a mix.
- Shallow boxcar scars often soften with fractional CO2 laser or RF microneedling. Deep boxcar scars usually need focused methods as well, such as TCA CROSS placed into each scar, subcision where the base is tethered, or punch techniques from a skin surgeon.
- Expect several sessions over months, with collagen remodelling continuing for three to six months after each one. Realistic results are softer edges and shallower scars, not erased scars, and results vary between people.
- In Asian skin, post-inflammatory hyperpigmentation (PIH) is the main risk, so settings are cautious and sun protection strict. At SkinRev Lab, CityLink Mall, and IN Eternity Clinic, Pacific Plaza, Dr Sin Yong treats boxcar scars with S3 Resurfacing, RF microneedling and 4D Scar Reconstruction, priced at consultation.
Watch · Dr Sin Yong explains
The scar
What boxcar scars are
Boxcar scars are atrophic, or depressed, scars: the skin sits lower than the skin around it because collagen was lost while an inflamed acne spot healed. They are round or oval, with steep, well-defined walls and a fairly flat floor, a little like a small crater. Chickenpox can leave similar scars.
In 2001, Jacob, Dover and Kaminer grouped atrophic acne scars into three types, ice pick, rolling and boxcar, because each shape responds to a different procedure. Ice pick scars are narrow, deep pits under about 2 mm wide; rolling scars are broad, soft dips with sloping edges, pulled down by fibrous bands; boxcar scars sit in between, wider than ice picks and sharper-edged than rolling scars.
Flat brown or red marks after acne are not scars. They are colour, not structure, and usually fade over months. If the skin is level when you run a finger across it, it is a mark.
Depth
Boxcar scars: shallow or deep changes the plan
Shallow boxcar scars, roughly under half a millimetre deep, mainly need their edges softened and the surrounding texture blended. Resurfacing and collagen-building treatments do this well. Deep boxcar scars are harder: resurfacing can smooth the rim but may not lift the floor, so a method that works inside each scar is usually added.
Some boxcar scars are also tethered at the base by fibrous strands, like rolling scars. A simple check is to stretch the skin gently between two fingers: a tethered scar softens a little, while a pure boxcar or ice pick scar mostly stays. Shining a phone torch from the side of the face, almost parallel to the skin, shows boxcar scars as crisp-edged shadows.
These home checks help you describe your scars, but the plan comes from an examination under angled light, where each scar is mapped by type and depth.
Shallow boxcar
Treating shallow boxcar scars: fractional CO2 or RF microneedling
Fractional CO2 laser vaporises microscopic columns of scarred skin and heats a thin zone around each one; bridges of untouched skin between the columns speed healing, and new collagen forms over the following months. RF microneedling instead carries radiofrequency heat through fine needles to a set depth, remodelling collagen while sparing more of the surface. With insulated needles, such as on the Secret RF system Dr Sin Yong uses, heat is released mainly at the tips.
The only direct randomised comparison treated matched areas in 15 patients with one session of each. Both gave the same median one-point improvement in scar texture at three months; CO2 caused more redness and skin disruption in the first days, while RF microneedling was rated more painful. In a Thai study of 26 people with skin types III to V who completed three monthly RF microneedling sessions, the largest group reported 26% to 50% improvement at six months, with only transient pigment change.
So the choice is more about skin type, scar depth and how much downtime you can take than about one device being stronger. For some shallow scars, Dr Sin Yong's non-ablative FSX Laser is a gentler alternative.
S3 Resurfacing
S3 Resurfacing: fractional CO2 planned scar by scar
S3 Resurfacing is Dr Sin Yong's multi-depth fractional CO2 laser protocol for acne scars, performed on the DEKA Tetra Pro (10,600 nm). Rather than one even pass over the face, it works in three phases within a session: precise point-shots placed into individual scar pits to soften their edges and floors; a fractional pass across the scarred zones at depths and densities set by the scar map; and a third pass for further collagen stimulation with tightening across the treated area.
Because the Tetra Pro sets depth and density separately, a deep boxcar scar and the normal skin beside it can receive different settings in the same session. That is why it is often used for boxcar scars with defined edges or depth, and for scars that have plateaued after other treatment.
The trade-off is recovery: numbing cream for 45 to 60 minutes beforehand, skin that feels hot and tight like strong sunburn, swelling that often peaks over the first three days, and fine crusts that flake by about day five to seven, followed by pinkness that fades over weeks. It also carries a higher risk of PIH in Asian skin than RF microneedling.
Deep boxcar
Deep boxcar scars: TCA CROSS, subcision and punch techniques
TCA CROSS (chemical reconstruction of skin scars) places a tiny amount of high-strength trichloroacetic acid into the floor of each narrow or deep scar, so that new collagen forms inside it over the following months. In the original study of 65 patients with Fitzpatrick IV to V skin, 82% of those treated with 65% TCA and 94% of those treated with 100% TCA had a good clinical response, without significant complications. In a later study of 53 patients treated with 70% TCA CROSS, 66% improved by more than half, and patients with predominantly boxcar scars did better.
Subcision passes a fine needle or blunt cannula under a scar to cut the fibrous bands tying it down. It is mainly a rolling-scar treatment, but boxcar scars with a tethered base can lift partly after it. Bruising is the main downtime and usually settles within one to two weeks.
For deep boxcar scars with a normal-looking floor, punch elevation lifts the scar floor to the surface; punch excision removes a scar and closes the skin with a fine stitch. These are minor surgical procedures offered by doctors trained in skin surgery, such as dermatologists and plastic surgeons. They are not part of Dr Sin Yong's 4D Scar Reconstruction; if they suit your scars, a referral can be discussed.
Combination
Why a combined plan, and what 4D Scar Reconstruction is
Few faces have only one scar type, and each type responds to a different tool. A 2026 network meta-analysis of 56 randomised trials in moderate-to-severe atrophic acne scars found that combination therapies generally did better than single treatments, with fractional CO2 combined with subcision among those with the steadiest benefit. The trials were mainly small split-face studies, so these are patterns rather than firm rankings.
4D Scar Reconstruction is Dr Sin Yong's combined protocol for depressed acne scars. Each scar is assessed and matched to the method that addresses its structure, using up to four tools: subcision for tethered scars, TCA CROSS for narrow, deep scars, fractional CO2 laser using the Tetra Pro S3 approach for the surface and edges, and, where volume has been lost, an injectable to support the scar floor. Not every patient needs all four.
Sequence matters. Active acne is controlled first, tethered scars are released before resurfacing, and sessions are spaced to let the skin heal and remodel. Leftover redness or brown marks can be treated separately.
Sessions
How many sessions, and what the downtime looks like
Collagen remodelling is slow. After laser, RF microneedling, subcision or TCA CROSS, change continues for three to six months, so sessions are spaced weeks to months apart and progress is reviewed before more is added. People with moderate scarring often need several sessions in total, across six months to a year. No number is promised in advance; the scar map and how your skin responds decide it.
Swelling in the first days can make scars look better than they will settle, so early photos mislead. Compare photos taken in the same light and position, a few months apart.
The table below shows typical patterns, not promises; your own downtime depends on the settings, the area and your skin.
| Method | Role for boxcar scars | Typical downtime | Typical course |
|---|---|---|---|
| S3 Resurfacing (fractional CO2) | Edges and floor of shallow and deep boxcar scars; surrounding texture | About 5 to 7 days of swelling and fine crusts; pinkness for weeks | Several sessions, spaced weeks apart once skin has settled |
| RF microneedling | Shallow boxcar scars and texture, especially in skin that darkens easily | Redness and mild swelling for 1 to 3 days | A series, often about a month apart |
| TCA CROSS | Narrow or deep boxcar scars, one scar at a time | Small dark crusts for about a week; pinkness for weeks | Often three to six sessions in studies |
| Subcision | Boxcar scars with a tethered base | Bruising for one to two weeks | One to three sessions, then energy treatments |
| Punch elevation or excision (dermatologist or plastic surgeon) | Individual deep boxcar scars | Stitches or a small graft for about a week | Usually once per scar, often smoothed later |
Asian skin
Darker skin and PIH: how the risk is kept down
Post-inflammatory hyperpigmentation, temporary darkening after skin injury, is the commonest setback when treating scars in Asian and darker skin. A study of fractional resurfacing in Chinese patients found that energy and density settings affected PIH, and that localised PIH occurred around the mouth in patients who did not receive air cooling. PIH usually fades over weeks to months, but it can be frustrating.
Because RF microneedling releases the bulk of its heat below the surface, it is often chosen first for skin that darkens easily, while fractional CO2 remains an option with cautious, tested settings. TCA CROSS also causes PIH in some people with darker skin, which is why skin preparation and careful technique matter.
Expect conservative settings, and sometimes a test area, at the first session. Do not treat while tanned or sunburnt, pause exfoliating acids, scrubs and retinoids for about a week before if advised, use broad-spectrum sunscreen daily throughout, leave crusts alone, and report any new darkening early. If you have recently taken isotretinoin, the timing of treatment is decided with your doctor.
Expectations and safety
Realistic results, risks and who should wait
Boxcar scars can usually be made shallower and less noticeable, but not erased. A review using the acne scar classification found few high-quality studies and many different scoring scales, which makes published percentages hard to compare. Be wary of anyone promising complete removal or a fixed result in one session.
Risks depend on the method: PIH, prolonged redness, infection or a cold sore flare after laser, bruising and small lumps after subcision, and, with too much acid, a widened scar or a pale mark after TCA CROSS. Raised scars and keloids are planned differently, because ablative injury and needling can provoke them.
Treatment is usually delayed with active acne, pregnancy, active infection or cold sores, bleeding disorders, a strong tendency to keloids, or a fresh tan. For very severe scarring, scars that need surgical revision, or raised scars, a dermatologist or plastic surgeon is the right next step. Choosing no treatment, or camouflage make-up, is also reasonable.
At SkinRev Lab
Boxcar scar treatment at SkinRev Lab: consultation and pricing
Boxcar scars are assessed and treated by Dr Sin Yong (MBBS Singapore, MRCS Edinburgh, MSc Practical Dermatology Cardiff). At consultation he examines your scars under different lighting angles, maps each one by type and depth, and checks your skin type, acne control, pigment history and medicines.
He then explains which methods each area needs, the order they would be done in, the expected downtime and realistic improvement. Options include S3 Resurfacing, RF microneedling, 4D Scar Reconstruction, referral for punch techniques where they suit, or no treatment. SkinRev Lab's non-invasive SKINTIGHT can soften surface texture with less recovery, but it does not reach scar collagen in the dermis. Medical treatment is priced at consultation, because the plan depends on how many scars there are, which methods suit them and how many sessions are needed.
Consultations are at SkinRev Lab, #B1-28 CityLink Mall, 1 Raffles Link, Singapore 039393, linked underground to City Hall and Esplanade MRT, open daily 11am to 8pm (WhatsApp +65 8266 9585), and at IN Eternity Clinic, 9 Scotts Road, #12-01 Pacific Plaza, beside Orchard MRT, Monday to Saturday (WhatsApp SkinRev Lab on +65 8266 9585 or IN Eternity Clinic on +65 8815 3008).
Sources
References & sources
- Jacob CI, Dover JS, Kaminer MS. Acne scarring: a classification system and review of treatment options. J Am Acad Dermatol. 2001;45(1):109-117.
- Boen M, Jacob C. A review and update of treatment options using the acne scar classification system. Dermatol Surg. 2019;45(3):411-422.
- Hendel K, Karmisholt K, Hedelund L, Haedersdal M. Fractional CO2-laser versus microneedle radiofrequency for acne scars: a randomized, single treatment, split-face trial. Lasers Surg Med. 2023;55(4):335-343.
- Vejjabhinanta V, Wanitphakdeedecha R, Limtanyakul P, Manuskiatti W. The efficacy in treatment of facial atrophic acne scars in Asians with a fractional radiofrequency microneedle system. J Eur Acad Dermatol Venereol. 2014;28(9):1219-1225.
- Lee JB, Chung WG, Kwahck H, Lee KH. Focal treatment of acne scars with trichloroacetic acid: chemical reconstruction of skin scars method. Dermatol Surg. 2002;28(11):1017-1021.
- Agarwal N, Gupta LK, Khare AK, et al. Therapeutic response of 70% trichloroacetic acid CROSS in atrophic acne scars. Dermatol Surg. 2015;41(5):597-604.
- Chan HH, Manstein D, Yu CS, et al. The prevalence and risk factors of post-inflammatory hyperpigmentation after fractional resurfacing in Asians. Lasers Surg Med. 2007;39(5):381-385.
- Ou Y, An G, Liang J, et al. Laser, microneedling, and combination therapies for moderate to severe acne atrophic scars: a systematic review and network meta-analysis. Aesthetic Plast Surg. 2026;50(17):7308-7334.
Common questions
Your questions,
answered
Can boxcar scars be removed completely?
Usually not. Treatment can make them shallower, soften their edges and blend them with the surrounding skin. Improvement is usually gradual, over several sessions, and results vary.
What is the difference between boxcar and rolling scars?
Boxcar scars have sharp, vertical edges and a flat floor. Rolling scars are broad, soft dips with sloping edges, pulled down by fibrous bands, and they soften when the skin is stretched. Many faces have both.
Which treatment suits shallow boxcar scars?
Fractional CO2 laser and RF microneedling both soften shallow boxcar scars. In a split-face trial, one session of each gave similar improvement at three months; RF microneedling is often chosen first for skin that darkens easily.
How are deep boxcar scars treated?
Usually with a combination: TCA CROSS inside each scar, subcision if the base is tethered, and fractional CO2 for the edges. Punch elevation or excision by a dermatologist or plastic surgeon suits some individual deep scars.
How many sessions do boxcar scars need?
Several, spaced weeks to months apart, because collagen keeps remodelling for three to six months after each session. Many people need treatment across six months to a year. The number is not fixed in advance.
What is the downtime for boxcar scar treatment?
It depends on the method: about five to seven days of swelling and fine crusts after fractional CO2, one to three days of redness after RF microneedling, about a week of small crusts after TCA CROSS, and one to two weeks of bruising after subcision.
Is boxcar scar treatment safe for darker skin?
It can be, with cautious settings. PIH is the main risk; RF microneedling spares more of the surface, and CO2 settings, skin preparation and strict sun protection lower the risk. A test area may be done first.
Do creams or facials fix boxcar scars?
No. Creams and facials can improve surface texture and marks, but boxcar scars are a loss of collagen in the dermis, and changing their structure needs a medical procedure.
Should my acne be clear before scar treatment?
Yes. Active acne should be controlled first, or new scars keep forming and inflamed skin is more prone to complications. If you have recently taken isotretinoin, the timing is decided with your doctor.
How much does boxcar scar treatment cost at SkinRev Lab?
It is a medical treatment by Dr Sin Yong and is priced at consultation, after the scars are mapped, because the cost depends on the methods, the area and the number of sessions.