A raised scar after an injury has healed.

A keloid is a raised scar after an injury, such as acne or a surgical incision, has healed. It's often lumpy or ridged. It's caused by too much of a protein called collagen in the skin during healing.

A keloid scar may form months to years after an injury. Symptoms may include thick, irregular scarring or an area of shiny, hairless, lumpy raised skin.

Keloids aren't harmful and don't need treatment. If a person finds them unattractive, a doctor or other health care professional can sometimes make the scar smaller.