Within those two categories, there are four types.

• Ice pick scars are narrow, deep holes that look like large pores. They develop after an infection (like cystic acne) works its way up from below the surface, leaving a column of damaged tissue.
• Rolling scars are sloping depressions created by fibrous bands pulling on the epidermis from deeper down, giving the skin an uneven, wavy look. They’re most common in areas where the skin is thicker, like the lower cheeks and jaw.
• Boxcar scars are round and pitted, with defined edges—similar to chickenpox scars. They’re left behind when inflammation destroys collagen. Without this structural support, the skin sinks in.
• Keloid scars are hypertrophic (raised) areas created by an overproduction of collagen during the wound-healing process. They look like raised bumps and can extend beyond the area of the original wound.

Injury and inflammation from acne can also cause increased pigment production that results in post-inflammatory hyperpigmentation (PIH). Most common in people with olive and brown skin, these flats spots of color (red, purple, brown, or black) occur when skin irritation triggers excess melanin production.