Acne scars form when inflamed breakouts damage the deeper layers of skin, and the body’s repair process produces too much or too little collagen to fill the wound properly. About 43 percent of people with acne develop some degree of scarring, and in 80 to 90 percent of those cases, the scars are the indented, pitted type caused by a net loss of collagen in the skin.
How Inflammation Leads to Scarring
Not every pimple leaves a scar. The difference comes down to how deep the inflammation reaches and how your body heals afterward. A mild whitehead stays near the surface, resolves quickly, and the skin rebuilds itself almost perfectly. But when a cyst or deep nodule ruptures beneath the surface, it destroys collagen and surrounding tissue in the dermis, the thick middle layer of skin that gives it structure. Inflammatory cells have been found in 77 percent of indented acne scars, which tells us the immune response itself is a major driver of the damage.
Your skin heals in roughly three stages. First, an inflammatory phase lasting several days, where the body rushes blood and immune cells to the wound to clear bacteria and debris. Then a rebuilding phase lasting several weeks, where new tissue and blood vessels form. Finally, a remodeling phase that starts around week three and can continue for up to 12 months, during which the body reorganizes collagen and contracts the wound. The repaired skin never fully matches the original. Even in normal wound healing, the healed area reaches only about 80 percent of its original strength.
Scarring happens when this process goes wrong. If the body produces too little collagen during repair, you get a depression or pit in the skin. If it overproduces collagen, you get a raised, thickened scar. The vast majority of acne scars fall into the first category.
Types of Indented Scars
Dermatologists classify indented (atrophic) acne scars into three types based on their shape and depth. Knowing which type you have matters because each responds differently to treatment.
- Ice pick scars are narrow, less than 2 mm wide, and extend deep into the skin in a V shape. They look like the skin was punctured with a small sharp instrument. Because they reach into the deepest layers, they’re often the most stubborn to treat.
- Boxcar scars are wider, round or oval depressions with sharp vertical edges, similar to chickenpox marks. Think of a U shape with a wide, flat base. They can be shallow or deep.
- Rolling scars are typically wider than 4 to 5 mm and caused by bands of scar tissue pulling the surface skin downward from underneath. This creates a wave-like, undulating texture across the skin rather than distinct pits.
Most people with acne scarring have a mix of all three types, which is one reason treatment plans often combine multiple approaches.
Raised Scars and Keloids
In a smaller number of cases, the body deposits too much collagen at the wound site. This creates raised, firm scars. Hypertrophic scars stay within the borders of the original breakout. Keloids go further, growing beyond the original wound as reddish-purple nodules made of dense, disorganized collagen bundles. Keloids are more common on the chest, shoulders, and jawline, and they occur more frequently in people with darker skin tones.
Why Some People Scar and Others Don’t
Two people can have equally severe acne and walk away with very different skin. Several factors explain the gap.
Severity and depth of breakouts. The more inflamed and deep-seated the acne, the more tissue destruction occurs. Superficial blackheads and whiteheads rarely scar. Deep cysts and nodules frequently do.
How long acne goes untreated. This is the single most important factor you can control. Multiple studies have found that the longer the gap between acne onset and effective treatment, the higher the likelihood of permanent scarring. Every month of uncontrolled inflammation gives the skin more opportunities to heal poorly.
Repeated flare-ups. Relapsing acne compounds the damage. Each new cycle of inflammation in the same area breaks down collagen that may have only partially recovered from the last round.
Genetics. Your genes influence how your body produces and breaks down collagen during wound healing. Researchers have identified specific genetic variants in enzymes responsible for collagen turnover that are linked to higher scarring risk. One variant, found in a study of a Chinese Han population, was significantly associated with both the likelihood and severity of acne scarring. If your parents or siblings scarred easily from acne, you probably will too.
Gender. Male sex is an independent risk factor for acne scarring, likely related to the role of androgens in driving more severe, inflammatory acne.
Age at onset. Developing acne at a younger age has been associated with greater scarring risk, possibly because adolescents are less likely to receive prompt treatment and because hormonal acne in younger patients tends to be more persistent.
How Picking and Squeezing Makes It Worse
Squeezing a pimple feels productive in the moment, but it forces inflamed material deeper into surrounding tissue, spreading the damage sideways and downward. This turns what might have been a surface-level breakout into a deeper wound with a higher chance of scarring. Picking can also introduce bacteria from your hands, causing secondary infection that prolongs inflammation and increases tissue destruction.
For some people, picking becomes compulsive, a condition dermatologists call acne excoriée. The scarring in these cases often looks disproportionate to the original acne because the mechanical trauma from picking is doing more damage than the breakouts themselves.
The Difference Between Scars and Dark Marks
Many people searching for information about acne scars are actually looking at post-inflammatory hyperpigmentation, the flat red, brown, or purple marks left behind after a breakout heals. These are not true scars. They involve changes in skin pigment, not structural damage to collagen. The key test: run your finger over the mark. If the skin is smooth and flat, it’s hyperpigmentation, and it will fade on its own over weeks to months (though sunscreen helps speed that process). If you feel a dip, bump, or textural change, that’s a scar, and it won’t resolve without intervention.
Why Early Treatment Matters So Much
Because scarring results from cumulative inflammatory damage, the most effective prevention strategy is controlling active acne as early as possible. Once a scar forms, the structural change to the dermis is permanent without cosmetic procedures. The collagen loss or overgrowth doesn’t reverse on its own.
This is especially important for moderate-to-severe acne. If over-the-counter products aren’t controlling your breakouts within a couple of months, that window of inflammation is widening. The American Academy of Dermatology recommends getting active acne under control before pursuing scar treatment, since new breakouts will just create new scars while you’re trying to fix old ones. Treating the acne itself is the first and most impactful step in preventing the scars you’re reading about right now.