Start here: is it even a scar?
Before working out which type of scar you have, it's worth establishing whether you have one. A large proportion of people searching for acne scar treatment don't — they have flat marks, which look similar in a mirror and need something completely different.
A scar is missing tissue. The skin surface is genuinely depressed, and it shows most in angled light. A mark is discolouration on level skin. Same surface, different colour.
The fingertip test, then the stretch test
First — close your eyes and run a fingertip over the area. If you feel a dip, you have a scar. If the skin feels completely level and only the colour differs, it's a post-inflammatory mark, not a scar. Those fade on their own or respond to pigment treatment.
Then, for anything you can feel — the stretch test. Place your fingers on either side and gently pull the skin taut.
Softens or disappears under tension — rolling scars. The pull is temporarily releasing fibrous bands tethering the skin down. This is the defining sign.
Unchanged, sharp edges intact — boxcar or ice pick. Structural defects in the skin itself, not tethering.
Some change, some don't — a combination, which is what most people have.
Five things it might be
Post-inflammatory erythema — flat red or purple marks from dilated capillaries — and post-inflammatory hyperpigmentation — flat brown marks from excess melanin. No tissue has been lost. Red marks generally fade over several months on their own. Brown marks are more persistent, particularly in deeper skin tones, and are the more common presentation there.
Fingertip test: skin feels completely level. This is the distinction that matters most, and it's the one most often missed.
A wavy, undulating surface without defined edges — the skin looks uneven across broad areas rather than pitted in distinct spots. Caused by fibrous bands beneath the skin pulling downward. The most common type, and the most reliably improvable when treated correctly.
Stretch test: softens or disappears under tension. If your scars visibly improve when you pull the skin, these are rolling scars.
Sharply defined vertical walls with a flat depressed base — like a stamp pressed into the skin. Angular edges stay visible under any lighting. Shallow ones respond well to resurfacing alone; deeper ones with a tethering component need subcision as well.
Stretch test: unchanged. The sharp edges are a structural defect in the dermis, not tethering.
Narrow, deep pinholes extending well into the dermis. Tiny in diameter but disproportionately deep — under magnification they look like punctures. Difficult because their depth exceeds what surface resurfacing can reach, and complete resolution is uncommon.
Stretch test: unchanged. Nothing at the surface alters a tract this deep.
Hypertrophic and keloid scars sit above the skin rather than below it — too much collagen rather than too little. More common on the chest, shoulders, and jawline than the cheeks. Firm, sometimes pink or darker, occasionally itchy.
Fingertip test: raised above the surrounding skin. If it's proud rather than depressed, everything on this page so far is the wrong approach.
A single face commonly has rolling scars across the cheeks, boxcar along the jaw, ice pick on the nose or chin, and flat marks scattered throughout.
That's why a plan built around the most visible type leaves the rest untreated — and why the useful question at consultation is which types are present and where, rather than which single treatment to book.
Matched to cause
| What it is | Actual cause | What addresses it |
|---|---|---|
| Flat red marks | Dilated capillaries | Time, sun protection |
| Flat brown marks | Excess melanin | Pico laser |
| Rolling | Fibrous tethering beneath | Subcision |
| Boxcar | Dermal tissue loss | Resurfacing |
| Ice pick | Deep narrow tract | Focal treatment, then resurfacing |
| Raised | Excess collagen | Corticosteroid injection |
Why resurfacing plateaus on rolling scars. Laser and RF microneedling work on the skin's surface and stimulate collagen in the dermis — genuinely useful. But neither releases fibrous bands pulling from beneath.
If you've had several sessions and improvement stopped short of what you expected, run the stretch test. Scars that soften under tension are still tethered, and subcision is the step that was missing. That pattern is the single most common thing that brings people in for a second opinion.
Which treatment is appropriate depends on Fitzpatrick type as much as scar type. Ablative CO2 carries meaningful post-inflammatory hyperpigmentation risk above Fitzpatrick III to IV — and using it on acne scarring in deeper skin can produce pigmentation worse than the scarring.
Subcision, RF microneedling, and microneedling are appropriate across all skin tones, since none of them delivers heat through the epidermis in the way ablative resurfacing does.
Deeper skin tones also develop post-inflammatory hyperpigmentation more readily from the acne itself, which is why the flat-marks-versus-scars distinction matters more here. More on device selection by skin tone.
What to do next
Do both tests, and note which scars change and which don't. That's genuinely useful information to arrive with — it tells a physician more than a description does, and it means the consultation starts from what you actually have rather than from what you thought you had.
If everything is flat and only the colour differs, you may not need scar treatment at all. That's a better outcome than a course of resurfacing for something that would have faded anyway.