Can Acne Scars Be Filled In? A Dermatologist Explains Acne Scar Types, Each Treatment, and Why the Choice Must Match the Scar
Acne scars (atrophic acne scars) are depressed scars that remain after inflamed acne has healed. They are among the hardest problems to treat in dermatology, because they represent a permanent loss of collagen in the dermis, not just dark or red marks that fade on their own. Many people mistakenly believe that one laser can treat every kind of acne scar, but in fact there are several types, and they respond very differently to treatment. Choosing a method that does not match the scar type wastes money and time and leads to disappointment. In this article, a dermatologist explains what causes acne scars, how many types there are, which treatment suits each type, and why "assessing the scar type first" matters more than choosing a laser device.
What causes acne scars?
Acne scars form when the inflammation of acne, especially deep inflammatory acne such as pustules, cysts and nodules under the skin, damages the collagen and elastin in the dermis. When the body cannot repair this damage completely, the skin sinks into a depression. Factors that raise the risk of acne scars include:
Severe or deep inflammatory acne that is left untreated for a long time
Picking or squeezing pimples, which increases inflammation and tissue damage
How long the acne stays inflamed, since the longer the inflammation lasts, the higher the risk
Genetics and each person's tendency to form scars
The key point is that acne scars are a permanent loss of tissue. This is different from post-inflammatory hyperpigmentation (PIH) and post-inflammatory erythema (PIE), which often fade on their own over time. Telling these apart before treatment matters, because dark and red marks do not need the deep procedures used for acne scars.
How many types of acne scars are there, and why tell them apart?
Acne scars fall into three main types based on their shape, and this is the core of choosing a treatment.
Ice pick (narrow, deep, needle-prick-like scars) have a narrow opening but go steeply deep into the dermis, with sharp edges. This is the type most resistant to general resurfacing lasers.
Boxcar (steep-edged, flat-bottomed scars) have a wider opening and clearly defined vertical edges, like a square pit. They can be shallow or deep.
Rolling (sloping-edged, wave-like scars) are caused by bands of fibrous tissue under the skin pulling the surface downward, which makes the skin look wavy, with indistinct edges.
The reason scars must be told apart is that each type responds to different methods. For example, rolling scars caused by tethering fibrous bands respond well to cutting those bands (subcision) but respond poorly to surface resurfacing alone. Deep ice pick scars usually need targeted acid application or excision rather than a laser passed over the whole face. In practice, most patients have several scar types mixed together, so a combination of methods is needed to get a good result.
How each type of acne scar is treated
The doctor chooses and combines methods according to the type and depth of the scars.
Subcision (releasing the fibrous bands under the scar) uses a needle or a special instrument inserted under the skin to cut the bands that pull the surface down. It is especially suitable for rolling scars, lifting the skin and stimulating new collagen.
TCA CROSS (targeted acid application) places high-concentration trichloroacetic acid into the scar pit only. It is suitable for ice pick scars and deep, narrow boxcar scars, and stimulates the base of the scar to build tissue and become shallower.
Punch techniques such as punch excision, which cuts out a deep scar and closes it with stitches, or punch elevation, which lifts the base of a boxcar scar level with the surrounding skin. They suit isolated deep scars that other methods have not helped.
Fractional laser and microneedling with RF stimulate collagen across the whole treated area. They suit improving overall skin texture and shallow scars, and are often used as a finishing step after deep scars have been dealt with by the methods above.
Fillers temporarily lift some types of scars or stimulate collagen, and are used as an add-on in some cases.
The doctor's guiding principle is to deal with deep scars and fibrous bands first using targeted methods, then refine the overall skin with laser or microneedling. Treatment usually takes several sessions spaced months apart, and results improve gradually rather than disappearing completely in a single session.
Realistic expectations
Most acne scars can improve clearly but do not disappear completely. A realistic goal is to make the scars shallower and the skin smoother to a level you are satisfied with, which generally takes several techniques combined and several sessions. Anyone who promises complete removal in one session is usually not being consistent with medical reality. In addition, any active acne should be calmed first, because as long as new inflammatory acne keeps appearing, more scars will keep forming.
Precautions, especially for Asian skin
Asian skin is prone to post-inflammatory hyperpigmentation (PIH) after procedures and lasers, so strict sun protection and following the aftercare instructions are essential, and the doctor will usually adjust laser strength to suit the skin tone. Treating too aggressively risks both dark marks and new scars. People with a history of raised scars or keloids should always tell the doctor beforehand.
What not to do
Do not believe advertising that claims one laser can treat every acne scar type in a single session.
Do not have acne scar procedures while active inflammatory acne is flaring. Calm the acne first.
Do not use strong caustic agents or peeling acids on your own to try to make scars shallower, as this risks wounds and dark marks.
Do not treat acne scars without having a doctor assess the scar type first, because choosing the wrong method will not work.
Frequently asked questions (FAQ)
Can acne scars be completely filled in?
Most acne scars can improve clearly but usually do not disappear completely, because the collagen loss is permanent. A realistic goal is shallower scars and smoother skin through several techniques combined over several sessions.
Is laser alone enough for acne scars?
It is usually not enough for deep scars, because ice pick and rolling scars respond only to a limited degree to lasers that treat the whole skin surface. The doctor therefore often uses subcision, TCA CROSS or punch techniques on deep scars first, then uses laser or microneedling to refine the overall skin.
How do the acne scar types differ?
Ice pick scars are narrow and deep like a needle prick, boxcar scars have steep edges and a flat base, and rolling scars have sloping, wave-like edges caused by tethering fibrous bands. Each type responds differently to treatment, so the doctor needs to assess them before choosing a method.
How many sessions does acne scar treatment take?
Generally several sessions are needed, spaced about a month apart or more, depending on the type, the depth and the method used. Results improve gradually and build up over time rather than appearing in a single session.
Are dark and red marks after acne different from acne scars?
Yes. Dark marks (PIH) and red marks (PIE) are marks where the skin surface is still smooth and they often fade on their own over time, whereas acne scars are a permanent depression in the skin. The treatments are therefore completely different.
Can acne scars be treated while I still have acne?
Active inflammatory acne should be calmed first, because if new acne keeps flaring, more scars will keep forming, and procedures on inflamed skin carry a higher risk of irritation and dark marks.
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed August 3, 2026
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