Boxcar Scars: Are 3-4 Laser Sessions Enough?

Boxcar scars are round or oval acne scars with sharp edges and a flat floor. Shallow ones often soften with a fractional CO2 laser alone, but deep boxcar scars with steep walls usually need another technique added on top.

That's why the plan starts with two questions, not a machine name: how deep is each scar, and is its floor tied down to the tissue underneath? In this article, we'll cover how to tell boxcar scars apart from ice pick and rolling scars, what the research says about laser sessions, and when other methods come in.

Quick summary

• Depth and a tethered floor decide what gets added to laser for boxcar scars.

• Session benchmark: in one fractional CO2 study, patients had 3-4 sessions 6 weeks apart, with results checked 6 months after the last one.

• Narrow, deep ice pick scars responded less to the same laser.

• Oozing or pus, pain that gets worse each day, or a scar that looks wider needs a call right away.

Boxcar Scar vs. Ice Pick vs. Rolling Scar: How Can You Tell?

Shine a light from the side. If you see a round or oval dent whose edge drops off like a step, it's a boxcar scar. Depressed (atrophic) acne scars are usually sorted into three shapes: ice pick, boxcar, and rolling.

Ice pick scars are narrow, V-shaped, and deeper than they're wide. They're the most common type, making up about 60-70% of atrophic acne scars. Boxcar scars come next: wider, round or oval, with distinct edges. Rolling scars are broad with soft, sloping edges, and they tend to smooth out when you stretch the skin.

Most faces have a mix of all three. Jotting down which scar is which shape makes it much easier to match each one to a treatment later.

How Many Sessions of CO2 Laser Do Boxcar Scars Need?

Shallow boxcar scars can respond to fractional CO2 laser* on its own. In a study of 60 people with atrophic acne scars who had 3-4 sessions spaced 6 weeks apart, 43.3% improved by more than half six months after the last session. Another 25% improved by a quarter to a half, and 31.7% improved by less than a quarter.

*Fractional CO2 laser: a laser that makes tiny, closely spaced columns in the skin so new tissue can fill in as it heals.

Rolling scars and shallow boxcar scars responded best, while deeper pitted scars responded least. That's roughly one in three people seeing less than a quarter of improvement. If you try to fix deep boxcar scars just by adding more laser sessions, you may spend a lot of time and still see less change than you hoped.

Keep in mind that scar treatment works in small steps. Each session tends to make scars a bit shallower rather than flattening them in one go, and individual results vary. Photos taken in the same light at the same angle are the fairest way to compare.

Deep Boxcar Scars: When Do Subcision, TCA CROSS, or Punch Get Added?

The first thing I look at is how deep the scar is and how sharp its edge is. If it's shallow with a gentle edge, a skin-regeneration treatment such as fractional CO2 laser or CureJet is usually where we start.

Next, I check whether the floor is stuck to the tissue below. If the scar doesn't flatten when the skin is stretched or pressed, and it feels anchored downward, that points to fibrous bands pulling on it. In that case, subcision* gets added to release them.

*Subcision: a fine needle is passed under the skin to cut the fibrous bands that pull a scar down.

For a scar with a small, deep opening, TCA CROSS is an option: a high-strength acid placed only inside the scar. On the other hand, a wide boxcar scar with a flat floor usually isn't helped enough by TCA CROSS alone, and it can carry a risk of widening edges or dark marks, so it's used less there. For very deep scars, punch elevation, where the scar floor is cut free and lifted level with the skin, can also be considered.

In a split-face study of 42 people, one side had laser alone and the other had punch elevation added. There was no difference at 1 month, but the punch side scored better at 4 months. So the scar gets broken down into its parts and treated in stages over several visits. Skin thickness, a tendency to darken after inflammation, any history of keloids, and active breakouts are all part of that plan too.

Side Effects and Downtime: What Passes and What Needs a Call

After fractional CO2 laser, redness typically lasts an average of 3-4 days and crusting about 4-6 days. In the 60-person study, 3 people developed post-inflammatory pigmentation (brown marks after inflammation) that lasted 8-12 weeks. If you have darker skin or old acne marks that stayed brown for a long time, let your provider know before treatment.

Never pick at scabs. If you notice any of the following, don't wait it out. Take a photo and contact the clinic right away.

• Oozing or pus, especially with an odor

• Redness, warmth, and pain that get worse day by day

• A treated area that looks wider or deeper than before

• Brown marks that come up quickly and look darker than your original scars

With TCA CROSS, acid that spreads into the surrounding skin can make a scar deeper. In one case report, a change in the application tool was followed by pain and dark marks, and two months later the scars looked more prominent. They improved after being re-treated with a fine needle. That's why this method relies on a tiny amount placed only inside the scar. If redness spreads or you develop a fever, seek medical care right away.

Treating Acne Scars on a Trip to Korea

Unless you had sedation that day, there's no need to postpone your flight home because of acne scar treatment. That said, redness and crusting can last several days, so it helps to schedule treatment away from days when you plan to take a lot of photos.

Acne scar treatment is built on a series of sessions, so a single visit doesn't complete the plan. Scars tend to get shallower step by step rather than changing a lot at once, and nobody can promise how much change you'll see or how long it lasts.

Once you're home, you can send photos to the clinic if something worries you. If there's pus, worsening pain, or another big change, see a local doctor first.

The Bottom Line: Take a Side-Lit Photo Before Your Consultation

To plan the order of treatment, it helps to know how many scars of each shape you have and which ones are tethered. Stand at a mirror with a light coming from the side and take a photo. Then stretch the skin with your fingers and mark which scars flatten and which don't. Note whether you're still getting new breakouts and whether you use any acne medication, oral or topical.

Before you decide, ask this: "Do my boxcar scars need subcision, or can we judge them by laser sessions first?" That one answer makes different treatment plans easier to compare.

Beautystone is a clinic in Seoul's Hapjeong area. When you reach out, include your side-lit photos, any acne scar treatments you've had before, and the dates you'd like to come in.

References

• How acne scars are classified as ice pick, boxcar, and rolling (J Am Acad Dermatol, 2001)

• Types of acne scarring and treatment options (DermNet)

• Fractional CO2 laser alone in 60 people with atrophic acne scars (J Cutan Aesthet Surg, 2014)

• 70% TCA CROSS in 53 people with atrophic acne scars (Dermatol Surg, 2015)

• Punch elevation added to fractional CO2 laser, 42-person split-face study (Indian J Dermatol, 2015)

• Subcision added to microneedle radiofrequency, 25-person split-face study (J Cosmet Dermatol, 2017)

• Case report of acne scars worsening after TCA CROSS (J Clin Aesthet Dermatol, 2021)