Laser and Skin

Acne scars: the shape decides the method

Acne scars can be improved, rarely erased, and the shape of the scar decides the method. Broad rolling and boxcar scars respond to fractional laser, microneedling and subcision, while narrow ice pick scars, 60 to 70 per cent of all atrophic acne scars, are too deep for surface methods and need point treatment with 65 to 100 per cent trichloroacetic acid or punch excision. Most series run to 3 to 6 sessions at intervals of 4 to 6 weeks, and the result is judged no earlier than 3 months after the last one.

Three scar shapes, three answers

Dermatologists sort depressed acne scars into three shapes, and each shape has its own mechanics. Ice pick scars are narrow, usually under 2 millimetres across, deeper than they are wide and V-shaped, running down into the deep dermis or below. They are the most common type, about 60 to 70 per cent of all atrophic acne scars. Boxcar scars are round or oval craters, typically 1.5 to 4 millimetres wide, with sharp, vertical edges; shallow ones sit 0.1 to 0.5 millimetres deep, deep ones go further. Rolling scars are the widest, often 4 to 5 millimetres or more, with soft, sloping edges, because fibrous bands under the skin pull the surface down. Most people carry a mix of all three on the same cheek.

The shape tells you where the problem sits. A rolling scar is held down from below, so it needs the bands cut (subcision) or the dermis rebuilt with microneedling. A boxcar scar is a matter of edges, so it needs resurfacing from above: fractional or ablative laser, a medium-depth peel or dermabrasion, which shave the rim and soften the step. An ice pick scar is too narrow and too deep for any surface method; the standard answers are chemical reconstruction, where 65 to 100 per cent trichloroacetic acid is placed into the pit with a fine applicator (TCA CROSS), or punch excision, where the scar is cut out with a 1 to 2 millimetre punch and closed with a single stitch.

Raised scars are a separate chapter. Hypertrophic scars stay within the outline of the original spot, keloids grow beyond it, and both are treated with steroid injections, silicone, pulsed dye laser or cryotherapy rather than with anything that removes tissue. If you want the general principles, scar treatment: improve, not erase covers them.

What lasers, needles and acids do

Fractional lasers fire thousands of microscopic columns into the skin per square centimetre and leave untreated skin between them. Those islands supply the repair, which is why a fractional ablative session heals in about 5 to 7 days, where full-field ablative resurfacing of the same area takes 10 to 14 days and carries a higher risk of lasting colour change. Non-ablative fractional systems heat the dermis without opening the surface, ask for 3 to 5 sessions instead of 1 to 2, and are the safer choice for darker skin.

Microneedling works mechanically. Needles of 1.5 to 2.5 millimetres (shorter lengths are for texture, not scars) open thousands of micro-channels that trigger collagen production over the following weeks. It is safe across all skin tones and is often combined with radiofrequency or platelet-rich plasma. Chemical peels dissolve the upper layers; for mild to medium strengths, expect 3 to 5 treatments given every 2 to 4 weeks, with 2 to 4 weeks of priming at home beforehand, and a higher pigmentation risk than needling. Fillers lift a rolling scar on the day, but most last only 3 months to 2 years.

All of these improve, none erase. A 2016 Cochrane review of 24 trials with 789 participants found moderate-quality evidence only for injectable fillers and low or very low-quality evidence for everything else, with no method proven superior as a first choice. That is not a reason to skip treatment, but it is a reason to distrust any promise of 100 per cent. Realistic is a visible softening over 3 to 6 sessions at 4 to 6 week intervals, more with combinations than with a single device.

The most important moment comes before the first session

As long as acne is active, new scars are forming, so the acne is treated first, without exception. About 95 per cent of people aged 11 to 30 have acne to some degree, and the scarring risk climbs with nodules, cysts and squeezing. Resurfacing an inflamed cheek is money spent against your own account; most dermatologists want the skin quiet for at least 3 to 6 months before the first session.

Two more waiting rules follow. If you have taken isotretinoin, laser resurfacing and dermabrasion wait at least 12 months after the end of the course, and your practitioner should hear about every acne treatment of the past 2 years, because retinoids, antibiotics and hormonal therapy change how the skin heals and how it reacts to light. Pregnancy is a reason to wait too, since most clinics postpone laser, TCA CROSS and punch excision until after birth, and a blood thinner such as aspirin or warfarin is worth mentioning before subcision or punch excision, both of which bruise and bleed more on these drugs.

And the red or brown marks that stay behind after a spot has healed are not scars. They are post-inflammatory colour changes without tissue loss, and most fade on their own within 3 to 12 months, faster with daily SPF 30 and a pigment inhibitor such as azelaic acid, slower in darker skin, where they can persist for 24 months. Waiting through this phase saves many an appointment, because a scar treatment does nothing for a mark.

How to recognise your scar shape

The simplest test uses side light. Stand at the mirror so that a lamp throws its light flat across the cheek from one side, at roughly 10 to 20 degrees above the skin. Narrow, deep points that look like puncture marks are ice pick scars. Clearly bordered, box-like depressions with a sharp rim are boxcar scars. Soft, wavy dents without a defined edge are rolling scars.

The second test is the stretch test. Pull the skin on both sides of the dent gently apart with two fingers. If the dent flattens out almost completely, it is a rolling scar held down from below, and subcision or needling will reach it. If it stays visible under tension, there is real loss of tissue, and the choice moves to resurfacing, filler or excision. Count as well as classify: 5 scattered ice pick scars are a job for TCA CROSS in 2 to 4 rounds, 50 of them across both cheeks call for a combination plan spread over 6 to 12 months.

This is why a device that treats every scar the same way misses two of the three shapes. A good consultation names each shape, estimates the number of sessions and puts a price on the whole series, not on a single visit.

Between the sessions, and what it costs

Sun protection is mandatory. Freshly treated skin darkens under UV and the discolouration can stay for months, so SPF 30 or higher goes on every day, including in winter, for at least 3 months after the last session. For the first 3 to 5 days after a session, use a fragrance-free, bland moisturiser and nothing else; then return to your usual routine step by step, and if you want that routine written down, the Routine Builder does it in 2 minutes. Pause retinoids and exfoliating acids for 3 to 5 days before and after each session, skip sauna and swimming for 48 hours, and skip sweaty sport for 24 hours. If you get cold sores, say so: ablative resurfacing and deep peels are usually covered with an antiviral from the day before until 7 to 10 days after.

Collagen remodelling is slow. The first change shows after 4 to 6 weeks, the result is assessed no earlier than 3 months after the final session, and the skin keeps changing for 6 to 12 months. Whoever is disappointed after the second session is judging too early.

On money: scar treatment counts as cosmetic almost everywhere, so public systems such as the NHS rarely cover it, and private prices for a full course run from around 400 to more than 10,000 pounds depending on the method. As a rough guide, a microneedling session costs 150 to 400 euros, a fractional laser session 300 to 900 euros, subcision 300 to 800 euros per area and TCA CROSS 100 to 300 euros per round. Multiply by the number of sessions before you compare offers, and ask what a touch-up costs after 12 months.

Before you book the first session

Frequently asked

Do acne scars disappear completely?

No. Realistic results are a visible softening over 3 to 6 sessions, and combinations of methods do better than a single device. Anyone promising perfectly smooth skin is promising too much.

Can I treat scars while my acne is still active?

No. As long as the inflammation runs, new scars form, so acne treatment comes first. Most practitioners want the skin quiet for 3 to 6 months before the first resurfacing session.

Are red marks after acne already scars?

Usually not. They are colour changes without tissue loss and fade on their own within 3 to 12 months, longer in darker skin. Daily SPF 30 speeds this up; a scar treatment does not.

How many sessions are usual?

For laser, microneedling and peels, mostly 3 to 6 at intervals of 4 to 6 weeks. Subcision and punch excision often need only 1 to 3. The exact number depends on the depth and count of the scars.

How long after isotretinoin can I have laser resurfacing?

Wait at least 12 months after the end of the course before ablative laser or dermabrasion. Tell the practitioner about every acne treatment of the past 2 years, because it changes how your skin heals.

How do I tell a rolling scar from a boxcar scar?

With side light and the stretch test. Pull the skin next to the dent gently apart: if it almost disappears, it is a rolling scar held down by bands under the skin. If it stays visible, there is real tissue loss, which points to a boxcar.

Sources

• American Academy of Dermatology: Acne scars, consultation and treatment · peel series of 3 to 5 treatments every 2 to 4 weeks, fillers lasting 3 months to 2 years, disclose acne treatments of the past 2 years
• DermNet: Acne scarring · classification of atrophic and raised scars, ice pick scars 60 to 70 per cent of atrophic scars, TCA CROSS with 65 to 100 per cent acid
• NHS: Acne, complications · three scar types, punch techniques and subcision, private prices from around 400 to more than 10,000 pounds; the parent page puts acne at about 95 per cent of people aged 11 to 30; reviewed January 2023
• British Association of Dermatologists: Acne, patient information leaflet · laser resurfacing not within one year of finishing isotretinoin, skin camouflage for pigment changes; updated July 2024

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This guide is for general information. It does not replace medical or professional cosmetic advice or an examination.