Causes

Experts don't completely understand what causes keloid scars. But most agree it's likely a dysfunction of the wound-healing process. Collagen — a protein found throughout the body — is useful to wound healing, but when the body produces too much, keloids can form.

Keloid growth might be triggered by any sort of skin injury — an insect bite, acne, an injection, body piercing, burns, hair removal, and even minor scratches and bumps. Sometimes keloids form for no obvious reason.

Keloids aren't contagious or cancerous.

A keloid is different from a hypertrophic scar. A hypertrophic scar stays within the bounds of the original wound and can fade over time without treatment.