What Causes Acne Scars? The Science Behind Scar Formation

Acne scars are caused by inflammation that damages the deeper layer of the skin (the dermis) during a breakout. As the body repairs that damage, it may lose collagen — leaving a depression — or, less commonly, lay down too much collagen, leaving a raised scar.

The deeper and more inflamed the acne, the more likely it is to scar. This is why early acne control matters, and why scar type should be assessed in person before any treatment plan is built.

An acne lesion begins when a pore becomes blocked with oil and dead skin cells, then colonised by bacteria. The body responds with inflammation — redness, swelling and the immune activity that breaks down the blockage.

That inflammation is necessary for healing, but it is also where the risk lies. When inflammation reaches deep enough to damage the dermis — the structural layer that holds collagen and elastin — the skin has to rebuild tissue rather than simply clear a surface spot.

A scar is what remains when that rebuild is imperfect. Most acne marks fade on their own; a true scar means the underlying structure of the skin has changed, which is why surface skincare alone usually cannot resolve it.

Collagen is the protein scaffold that gives skin its firmness and even surface. During an inflammatory breakout, immune cells release enzymes that break down damaged tissue — including healthy collagen caught in the area.

If the breakdown outpaces the skin's ability to rebuild evenly, the surface is left lower than the surrounding skin. The more intense and prolonged the inflammation, the more collagen can be lost, and the deeper the resulting depression tends to be.

An acne scar is essentially a wound-healing outcome. Healing happens in overlapping phases: inflammation, the building of new tissue, and remodelling, where collagen is reorganised over weeks and months.

How each phase plays out is influenced by the depth of the original lesion, how long it stayed inflamed, whether it was picked or squeezed, and individual healing tendencies. Picking or squeezing matters because it pushes inflammation deeper and prolongs it — increasing the chance of a lasting scar.

Because remodelling continues for months, fresh scars can look different a year later. This is one reason doctors often wait until acne has settled before assessing scars for treatment.

Acne scars fall into two broad groups depending on whether collagen was lost or overproduced during healing. The distinction matters because the two are treated in almost opposite ways.

Atrophic scars — depressions where collagen was lost — are by far the most common type after facial acne. Hypertrophic and keloid scars — raised areas of excess collagen — are seen more often on the chest, back and jawline.

Surface whiteheads and blackheads sit in the upper skin and rarely scar. Deep, inflammatory lesions — nodules and cysts — reach down into the dermis, where the structural collagen lives.

When inflammation occurs at that depth, there is more tissue to damage and a longer, more disruptive healing process. That combination is why cystic acne carries a much higher scarring risk than mild surface breakouts.

It also explains why two people with similar-looking acne can end up with very different skin: the depth and intensity of inflammation, not just the number of spots, drives scarring.

The most effective scar prevention is controlling active acne before it becomes deep and inflammatory. Reducing how often and how intensely the skin is inflamed reduces the cumulative damage to collagen over time.

Avoiding picking and squeezing, getting persistent or cystic acne reviewed early, and following a consistent treatment plan all help. Once scarring has formed it can still be improved, but prevention during the active phase is always the gentler route.

Scar treatment is usually considered once active acne is under control and the skin has had time to settle. Treating scars while breakouts are still flaring can irritate the skin and is not always the right starting point.

If marks or depressions have stayed largely unchanged for several months after acne calmed, that is a reasonable point to seek an assessment. Results vary between individuals, and a doctor will set realistic expectations for your specific scar type.

At DrPlus in Johor Bahru, an acne scar assessment starts with examining the skin in good lighting to identify which scar types are present and how they are distributed. Most people have a mix, so mapping the dominant pattern guides what is considered first.

The consultation also covers skin tone considerations, whether any active acne should be addressed first, realistic expectations, and likely number of sessions. You do not need to commit to any treatment on the day — a consultation is for understanding your options.