When acne lesions clear, they often leave behind marks. Many people use the term “acne scar” for any lasting spot, but this is often inaccurate. Not every lingering mark is a true scar; the distinction lies in whether the mark affects the skin’s color or its physical texture. Understanding this difference is crucial for effective treatment, as the underlying biological causes are separate. The most common post-acne mark is post-inflammatory hyperpigmentation (PIH), which results from the skin’s inflammatory response.
Discoloration Versus Textural Change
Acne scars are fundamentally different from post-inflammatory hyperpigmentation (PIH). The core distinction is that PIH is a change in color, while a true acne scar is a change in the skin’s physical structure and texture. When running a finger over PIH, the skin feels smooth, but a true scar will feel either depressed or raised.
PIH is considered a temporary mark, often fading over several months to a year. In contrast, a true acne scar represents a permanent alteration to the skin’s surface, typically involving the loss or excessive production of collagen. This structural change means true scars will not resolve without targeted medical intervention.
Understanding Post-Inflammatory Hyperpigmentation
Post-inflammatory hyperpigmentation is the skin’s response to inflammation caused by an acne lesion or other injury. The inflammatory process stimulates melanocytes, the cells responsible for producing pigment. This stimulation causes an overproduction of melanin, which is then deposited in the epidermis or dermis.
The appearance of PIH is typically a flat patch of discoloration that ranges from light brown to black, depending on skin tone and pigment depth. If the excess melanin remains in the epidermis (the skin’s outermost layer), the spots tend to be brown and fade more quickly.
If the inflammation is severe, the melanin can drop into the dermis (the deeper layer), where it is engulfed by immune cells called melanophages. This deeper dermal pigmentation often appears blue-gray and is far more stubborn and long-lasting than epidermal PIH. Sun exposure significantly intensifies and prolongs its presence.
Types of True Acne Scars
True acne scars result from the body attempting to heal deep inflammatory lesions, leading to either too little or too much collagen production. The most common types are atrophic, or sunken, scars, which occur due to a net loss of tissue beneath the skin’s surface. Atrophic scars are categorized by their shape and depth.
Ice pick scars are narrow and deep, resembling a V-shaped puncture that extends into the deeper dermal layers. Boxcar scars are broader depressions with sharp, well-defined vertical edges, giving them a square or crater-like appearance. These typically result from significant collagen destruction over a wider area.
Rolling scars are the third major atrophic type, presenting as shallow, wavy undulations with ill-defined, sloping edges. They are caused by fibrous bands of tissue that form between the skin and the subcutaneous layer, pulling the skin’s surface downward. Less common are hypertrophic scars and keloids, which are raised scars resulting from an overproduction of collagen.
Targeted Treatments for Each Condition
Because PIH and true scars have different origins, they require distinct treatment approaches. PIH treatments focus on inhibiting melanin production and speeding up the turnover of pigmented skin cells. Topical retinoids, such as tretinoin and adapalene, accelerate cell exfoliation to shed pigmented cells quickly.
Ingredients like hydroquinone block the enzyme tyrosinase, which is necessary for melanin synthesis, effectively lightening dark spots. Other helpful topical agents include azelaic acid, which decreases inflammation, and Vitamin C, an antioxidant that inhibits melanin production. Professional treatments often involve light chemical peels or laser procedures designed to target and break up the excess pigment.
Treatments for true acne scars, particularly atrophic ones, must physically restructure the collagen in the dermis. Professional procedures like micro-needling create controlled micro-injuries to stimulate the production of new collagen and elastin, improving the skin’s overall texture. Subcision is a technique used specifically for rolling scars, involving a needle inserted beneath the skin to break the fibrous bands that tether the surface down. Dermal fillers are also used to raise depressed scars, while ablative fractional lasers remove micro-columns of tissue for resurfacing.