Acne Scars: Types, Causes, and What You Should Know
Acne scars are marks left on the skin after blemishes heal. They form when the skin’s repair process is disrupted — producing too much or too little collagen in response to inflammation. The type of scar you develop depends on how your skin heals, not simply on how severe the original spot appeared.
This page covers how scars form, the different types, how severity is graded, and the factors that shape how they respond to treatment. It is written by Dr Justin Boey, Medical Director of Sozo Aesthetic Clinic, as a resource to help you understand your skin before exploring options.
How Do Acne Scars Form?
Acne scars occur when the skin fails to repair itself adequately after an inflammatory breakout. Blackheads and whiteheads rarely cause scarring. It is the deeper, inflamed lesions — papules, pustules, nodules, and cysts — that cause lasting damage to the surrounding tissue.
When these lesions resolve, the skin attempts to rebuild. This involves collagen production — the structural protein that gives skin its support and volume. The problem is that this process is rarely exact.
- Too little collagen produced: the skin heals below its original surface level, leaving a depression. These are atrophic, or depressed, scars — the most common type seen in acne patients.
- Too much collagen produced: the skin heals above its original surface level, creating a raised mass. These are hypertrophic or keloid scars.
The severity of scarring is influenced by the depth of the inflammation, how promptly the acne was treated, and genetic factors that determine how aggressively your skin responds to injury. Some people scar more readily than others, regardless of how carefully they manage their skin.
Picking or squeezing spots significantly worsens outcomes. It forces bacteria deeper, prolongs the inflammatory response, and ruptures the skin barrier. The resulting immune reaction is more intense — and the scarring more likely.
Timing matters more than most people realise. Leaving active spots untreated for extended periods gives inflammation time to deepen, increasing both severity and the likelihood of permanent structural damage. Treating acne early — before it progresses to cysts or nodules — is the single most effective way to reduce scarring risk.
Types of Acne Scars
Acne scars fall into two broad categories: atrophic (depressed) scars and raised scars. Atrophic scars are by far the more common outcome of inflammatory acne. Within each category, specific subtypes have distinct appearances, depths, and treatment implications.
Rolling/Atrophic Scars
Rolling scars create a wave-like, undulating texture across the skin surface. They form when fibrous tissue bands develop between the dermis and the deeper subcutaneous tissue. These bands physically tether the skin downward, producing the rolling or draped appearance.
They often look more pronounced in raking or directional light. The underlying tethering means they do not respond to surface resurfacing alone — the fibrous attachment needs to be mechanically released before the skin can lift.
Ice Pick Scars
Ice pick scars are narrow, deep, and sharply defined. They penetrate well below the skin surface — often reaching into the dermis — and resemble small open pores or puncture marks. Because of their depth, they are among the more technically demanding scar types to treat. Superficial resurfacing alone is rarely sufficient.
They are most commonly caused by severe inflammatory acne, particularly cystic lesions that have infected the skin deeply.
Boxcar Scars
Boxcar scars are broad depressions with sharp, well-defined vertical edges and a flat base. They form when localised inflammation destroys a volume of collagen, leaving the skin with a clearly outlined divot. They range from shallow to deep and appear most frequently on the cheeks and temples.
Shallow boxcar scars tend to respond well to resurfacing-based treatments. Deeper ones usually require a combination approach.
Keloid Scars
Keloid scars are raised, irregular, and extend beyond the boundary of the original acne lesion. They result from an aggressive healing response in which collagen continues to be deposited well after the wound has closed. Keloids can be tender or itchy and may continue to grow over time.
They are more prevalent in individuals with darker skin tones (Fitzpatrick types IV–VI) and often have a familial pattern, suggesting a genetic component. They are among the most difficult scar types to manage and typically require a specialist approach.
Hypertrophic Scars
Hypertrophic scars are raised, firm, and thickened. They result from an overproduction of collagen during the healing process, which builds tissue above the original skin level. Unlike keloids, they remain within the boundary of the original lesion and do not spread to surrounding skin.
They are more common on the chest, shoulders, and upper back, and less frequently on the face. Some hypertrophic scars soften with time; others persist without intervention.
A note on post-acne marks: Post-inflammatory hyperpigmentation (PIH) and post-inflammatory erythema (PIE) are flat marks — dark spots and red or pink marks respectively — that can follow an acne breakout. These are not structural scars. They result from excess melanin production (PIH) or dilated blood vessels (PIE) during healing. Dark spots and brown marks can take three to 24 months to fade, and the process is slower in individuals with darker skin tones or ongoing active breakouts. Unlike atrophic or raised scars, they involve no structural tissue loss and can improve with time, consistent sun protection, and appropriate topical treatment. If you are unsure whether you have scars or post-acne marks, a clinical assessment will differentiate them.
How Severe Are Your Scars?
Severity grading is how clinicians move from a general impression — “these scars look bad” — to a structured, reproducible assessment that can guide treatment decisions and measure progress over time.
Scar Grading Scales
Several clinical grading systems exist. The Goodman and Baron Qualitative Grading Scale is one of the most widely referenced in published literature and clinical practice. It assesses scar severity on a four-grade scale based on visibility and response to skin stretching:
- Grade 1 — Macular: flat scars (red, pigmented, or pale). No surface change. Visible but not textural.
- Grade 2 — Mild atrophic or hypertrophic: visible at a social distance over 50 cm. Able to be covered adequately with make-up or the normal shadow of shaved beard hair.
- Grade 3 — Moderate: visible at a social distance under 50 cm. Partially flattened by manual skin stretching. Not easily covered with make-up.
- Grade 4 — Severe: not correctable by stretching. Visible at a distance of over 50 cm. Unable to be covered with make-up.
The acne scar grading system used at Sozo Clinic forms part of the initial assessment, alongside a physical examination of scar types, distribution, and skin tone.
Mild, Moderate, and Severe Scarring
Mild scarring typically involves Grade 1–2 lesions: surface-level textural changes, shallow depressions, or flat post-acne marks. The overall skin contour remains largely intact.
Moderate scarring involves a mix of scar types across multiple areas of the face, with some Grade 3 involvement. The skin has visible textural irregularity at normal conversational distance.
Severe scarring involves Grade 4 lesions with significant depth, often across broad areas. The overall skin contour is markedly altered. Treatment at this level typically requires a multi-session, multi-modality protocol over an extended period.
Understanding your grade helps set realistic expectations. No single treatment resolves severe acne scarring in one session. A staged approach — addressing tethering, volume deficit, and surface texture in sequence — is standard for moderate-to-severe presentations.
Why Acne Scars Don't Fade on Their Own
Post-acne marks — PIH and PIE — do fade with time, particularly with consistent sun protection and appropriate topical treatment. Structural scars do not.
Atrophic scars represent a physical deficit in the dermis. The collagen that once supported the skin’s surface has been destroyed and was not replaced during healing. The skin lacks the structural capacity to spontaneously regenerate this lost tissue. Without targeted intervention, the depression remains — and in many cases becomes more noticeable as surrounding skin ages and loses volume.
Raised scars persist for a different reason. Hypertrophic and keloid scars are composed of disorganised collagen fibres. Normal skin collagen has an organised, basket-weave architecture that provides flexibility and resilience. Scar collagen is dense and parallel — it does not remodel into normal skin architecture without intervention.
Rolling scars are held in place by fibrous bands beneath the skin surface. These bands physically anchor the skin downward to deeper structures. They will not release without mechanical disruption — no topical product or surface treatment reaches them.
Sun exposure worsens all scar types over time. UV exposure deepens pigmentation in PIH, increases the contrast of atrophic depressions, and accelerates collagen degradation in already-compromised skin. This is why sun protection is not optional in scar management — it prevents active worsening while treatment is under way.
What Affects Your Treatment Outcome?
Two patients with similar-looking scars can have very different responses to the same treatment. The variables below explain most of that difference.
Skin Type
Skin tone affects both the type of scarring that forms and the parameters that can be safely used during treatment. Individuals with darker skin tones (Fitzpatrick types IV–VI) are more prone to post-inflammatory hyperpigmentation — both from the original acne and as a potential side effect of certain laser treatments at inappropriate settings.
This does not mean effective treatment is unavailable for darker skin. It means the selection of technology and treatment parameters needs to be calibrated to the individual. Clinicians experienced in treating diverse skin tones will adjust energy levels, wavelengths, and recovery protocols accordingly.
Scar Age
Scars that are relatively recent — within the first 12 months of formation — still contain active remodelling processes within the dermis. Treatment during this window can leverage these processes, often producing faster and more significant improvement than the same treatment applied to older scars.
Mature scars are more fibrotic and less responsive. The tissue has stabilised, the collagen has organised, and the biological activity that would facilitate remodelling has ceased. Older skin also requires more collagen stimulation to smooth out textural irregularity, and accumulated sun exposure over the years can deepen pigmentation in scars — making them darker and more resistant to treatment. Addressing scars earlier, while the skin is still in an active remodelling phase, consistently produces better outcomes with fewer sessions.
Scar Depth
Superficial scars — Grade 1–2 atrophic scars and shallow boxcar scars — respond well to resurfacing-based treatments that target the upper dermis. Deeper scars, particularly ice pick scars and rolling scars with significant subdermal tethering, require treatments that reach deeper structures. An acne scar treatment guide can help clarify which approaches address which depths.
In practice, most moderate-to-severe presentations involve a mix of scar depths and types. A single-modality approach rarely addresses all components. Sequential treatment — mechanical release, volume restoration, and surface resurfacing — is the standard approach for complex presentations.
When Should You See a Doctor?
Topical products have a genuine role in acne scar management — particularly for PIH, PIE, and surface texture. But their reach is limited. They cannot structurally repair atrophic depressions, release subdermal tethering, or reduce raised scar tissue.
A clinical assessment is the appropriate next step if:
- You have been using topical treatments consistently for three months or more without meaningful improvement.
- Your scars are deep, raised, or affect more than isolated areas of the face.
- The scarring has been present for over a year with no visible change.
- PIH or PIE is not responding to consistent sun protection and topical lightening agents.
- The appearance of your skin is causing you distress that affects daily confidence or wellbeing.
An accurate clinical assessment identifies your scar types, grades their severity, evaluates your skin tone and response to inflammation, and determines which treatment combinations are most appropriate. Without this foundation, treatment selection is guesswork.
Early intervention — before scars fully mature — generally produces better outcomes and requires fewer sessions. If you have active acne alongside existing scars, managing the acne first is typically the priority before targeting the scarring.
Next Step: Acne Scar Treatment Options
Sozo Aesthetic Clinic offers a range of evidence-based treatments for acne scarring in Singapore, led by Dr Justin Boey, Medical Director. Each treatment plan is tailored to the individual’s scar types, skin tone, severity grade, and treatment goals — based on an in-person assessment. To explore the full range of procedures and what to expect during consultation, visit the acne scar treatments in Singapore page.
Ready to treat your acne scars?
Book a consultation: sozoclinic.sg/contact-us
WhatsApp Dr Boey’s team: 9610 5102
All acne scar treatment options: acne scar treatments at Sozo Clinic
Acne Scar Treatment
References
Clinical Studies
- Goodman GJ, Baron JA. Dermatologic Surgery. 2006;32(12):1458–1466. — the qualitative grading scale cited in the body text. DOI linked.
- Connolly D, Vu HL, Mariwalla K, Saedi N. J Clin Aesthet Dermatol. 2017;10(9):12–23. — covers atrophic scar pathophysiology, collagen mechanisms, and scar classification. URL linked.
Official Guidelines
- Thiboutot D et al. AAD Guidelines of care for the management of acne vulgaris. JAAD, 2024. — the current standard-of-care guideline on acne, which includes scarring prevention as a core treatment endpoint. DOI linked.
