Acne Scar Types (Ice-pick, Boxcar, Rolling)

In short: Acne scars are permanent tissue changes that form in the skin as inflamed acne lesions heal. Depressed (atrophic) scars are the most common group and, under the Jacob classification, are divided into ice-pick, boxcar and rolling scars; raised (hypertrophic or keloid) scars are a separate group. Red or brown marks after acne are not true scars. The type and severity of scarring guide treatment choice; the aim is to improve appearance, not to erase the scar.

What is an acne scar?

An acne scar is a permanent structural change in the dermis that forms while inflammatory acne lesions (papules, pustules, nodules or cysts) heal. Inflammation damages the collagen and elastic fibres around the hair follicle and oil gland. If repair falls short, tissue is lost and a depressed (atrophic) scar forms; if repair is excessive, extra tissue builds up and a raised (hypertrophic) scar or keloid develops. Atrophic scars are considerably more common than raised scars.

The risk of scarring rises with deep and long-lasting inflammatory acne, with delayed treatment and with squeezing or picking lesions. For this reason, the most effective way to prevent acne scars is early and appropriate treatment of the acne itself. This page describes scar types and assessment; treatment methods and their levels of evidence are covered in detail under "Scar Treatment".

How do acne scars form?

The mechanism of acne scarring is not fully understood, but the basic process is well known. In an inflamed lesion the follicle wall is damaged, and inflammatory cells and the enzymes they release break down the surrounding connective tissue. Wound healing proceeds in three phases: inflammation, new tissue formation, and remodelling that lasts for months. If too little collagen is produced during this process, the surface sinks. If fibrous bands beneath the skin pull the surface downward, an undulating (rolling) appearance results. When collagen production is excessive, the scar becomes raised.

The depth and duration of inflammation largely determine the type and severity of the scar. Superficial inflammation often leaves only a temporary colour change, whereas deep nodular lesions more often lead to permanent tissue loss.

Types of atrophic acne scars (Jacob classification)

In 2001 Jacob, Dover and Kaminer proposed a simple classification describing three types of atrophic acne scar. It remains the most widely used system in clinical practice and in research.

• Ice-pick scars: Narrow (usually smaller than 2 mm), deep scars that taper downward. They can extend into the deep dermis and sometimes the subcutaneous tissue. Because the opening is narrow, treatments applied from the surface struggle to reach the base; they are among the most resistant types.
• Boxcar scars: Round or oval depressions with steep, sharp edges and a relatively flat base. They can be shallow or deep. Shallow boxcar scars usually respond better to treatment than deep ones.
• Rolling scars: Broader scars with gently sloping edges that give the surface an undulating look. They are caused by fibrous bands tethering normal-looking skin to deeper tissue. They stand out under side lighting and often flatten when the skin is stretched.

In everyday practice most people have more than one type at the same time. Some authors also describe additional subtypes such as sinus tracts or superficial atrophic macules. The real value of the classification is that each type reflects a different anatomical problem and therefore responds to a different approach.

Raised scars and colour changes that are not scars

• Hypertrophic scars and keloids: Raised acne scars are most common along the jawline and on the chest, back and shoulders. A hypertrophic scar stays within the borders of the original lesion; a keloid extends beyond them into surrounding healthy skin. Their management is completely different from that of depressed scars (see "Hypertrophic Scar").
• Post-inflammatory erythema (PIE): Pink or red marks left where a spot has healed. They come from small surface blood vessels. PIE is not a true scar and often fades on its own over months; if it persists, vascular laser or light options can be discussed.
• Post-inflammatory hyperpigmentation (PIH): Brown or dark marks. PIH is more common and longer-lasting in darker skin. It usually fades with consistent sun protection and suitable topical treatment, whereas a poorly chosen procedure can make it worse.

This distinction matters in practice: treating a red or brown mark as if it were a depressed scar exposes the patient to unnecessary risk.

How are acne scars assessed?

Acne scars are assessed during a physician consultation, which usually includes the following steps:

• Type and distribution: Scars in each facial area are typed separately. Side lighting and standardised photographs make rolling scars in particular easier to see and create a record for later comparison.
• Stretch test: Scars that flatten when the skin is stretched between the fingers (most rolling scars and some shallow boxcar scars) need a different approach from scars that do not (ice-pick and deep boxcar scars).
• Severity grading: In Goodman and Baron's qualitative system, grade 1 is macular (flat, colour change only); grade 2 is mild (not easily noticed at social distance, can be covered by make-up or a beard); grade 3 is moderate (obvious at social distance, flattens when stretched); and grade 4 is severe (does not flatten when stretched). The same authors' quantitative system scores scars by type and number; a small study reported good agreement between different observers. These scales are especially useful for comparing before and after treatment.
• Fitzpatrick skin type: Darker skin tones carry a higher risk of colour change after procedures, which directly affects the choice of method and settings.
• Active acne: If new inflamed lesions are still appearing, the acne is brought under control first. Otherwise new scars keep forming and the gains from scar treatment are reduced.
• Medicines and history: All medicines (including isotretinoin) and supplements, any history of cold sores, a tendency to keloids and previous procedures are reviewed.

Isotretinoin and timing of procedures

For many years a wait of 6–12 months after finishing isotretinoin was advised before procedures, but this practice rested on a small number of case series from the 1980s. A systematic review with consensus recommendations published in 2017 (Spring et al.) reported insufficient evidence to support delaying procedures such as superficial chemical peels, laser hair removal and fractional ablative and non-ablative lasers because of isotretinoin. The same report stated that mechanical dermabrasion and fully ablative laser are not recommended during isotretinoin treatment. An American Society for Dermatologic Surgery (ASDS) task force reached a similar conclusion for superficial peels and non-ablative devices.

This evidence is still limited, and product labelling can differ between countries. Which procedure is done and when is decided by the physician, together with the doctor who prescribed isotretinoin and based on an individual risk assessment. If you are taking isotretinoin or have recently finished it, always say so.

Approach by scar type and level of evidence

The summary below shows the approaches most often discussed for each scar type. Most of the evidence comes from small, uncontrolled or short-follow-up studies. Systematic reviews stress that the lack of a standard way to measure acne scarring makes studies hard to compare.

• Rolling scars: Subcision, which releases the fibrous bands, is the main option; it is often combined with microneedling, radiofrequency microneedling or filler. Level of evidence: moderate to low (many small clinical studies and reviews).
• Boxcar scars: Fractional ablative and non-ablative lasers and radiofrequency microneedling are used; punch techniques are considered for selected deep scars. The 2022 international consensus lists energy-based devices among first-line options for many acne scar types. Level of evidence: moderate (consensus and systematic reviews; few randomised trials).
• Ice-pick scars: Focal trichloroacetic acid application (TCA CROSS) or punch excision is used; the product, strength and technique are decided entirely by the physician. Level of evidence: low to moderate (mostly uncontrolled case series).
• Mixed types: A staged combination plan is usually needed, for example subcision first and a resurfacing method afterwards.

Darker skin and pigmentation risk

In Fitzpatrick skin types IV–VI, post-inflammatory hyperpigmentation is more common after lasers, peels and needle-based procedures. According to systematic reviews, ablative lasers may achieve the greatest efficacy but also carry more pain, longer downtime and a higher risk of long-term pigment change. Non-ablative fractional lasers and radiofrequency microneedling offer a safer side-effect profile, although their efficacy may be somewhat lower than that of ablative methods. In darker skin, more conservative settings, longer intervals between sessions, pigment control before and after treatment and strict sun protection are preferred; a small test area may be treated first where appropriate. People with a tendency to keloids need particular care in the choice of procedure.

Realistic expectations

Acne scars are not erased completely; the goal is a visible and meaningful improvement. The degree of improvement reported in studies varies widely by method and scar type, and several sessions and combined methods are usually required. Because collagen remodelling takes months, results appear gradually and the final assessment is usually made a few months after the last session. Scar depth and number, skin type and individual healing all influence the outcome; no method can guarantee a particular result.

When procedures are not appropriate and when to refer

• If active, inflamed or nodulocystic acne is not under control, acne treatment is planned first.
• If there is an active infection, cold sore or open wound in the treatment area, the procedure is postponed.
• Most elective procedures are postponed during pregnancy and breastfeeding.
• If expectations are unrealistic, or if the scars cause marked psychological distress, this is discussed openly and psychological support is suggested where needed.
• Raised scars or keloids, very extensive or severe scarring, deep scars that may need surgery, lesions with an uncertain diagnosis and severe acne are referred to dermatology or plastic surgery.

Tell your physician about all medicines and supplements you take, including blood thinners. Never stop a prescribed medicine without asking the doctor who prescribed it.

How this clinic approaches acne scars

At our clinic, acne scar assessment begins with a consultation with medical aesthetics physician Dr. Hamza Gemici. Scars are typed and photographed under standard lighting, and skin type, active acne and current medicines are reviewed. Possible methods, their levels of evidence, risks and limitations are discussed openly, and the plan is agreed jointly. Where there is active acne, raised scarring or a possible need for surgery, we work with dermatology or plastic surgery colleagues; if a procedure is not considered appropriate, we say so clearly.

Sources

This content is based on the classification by Jacob et al. (2001), the grading systems of Goodman and Baron (2006), the review by Fabbrocini et al. (2010), a systematic review of energy-based methods (Kravvas and Al-Niaimi, 2018), the 2022 international consensus (Salameh et al.) and the 2017 consensus reports on isotretinoin and procedure timing. Full citations are given in the reference list.