Why are scars permanent?

Our body has a wonderful mechanism. Every time you hurt yourself, fall off the bike, burn your hand, or pick at a pimple, the body quickly heals the open wound by forming a scar. And yet, many of these scars remain permanently to remind you of the injury.

As soon as the skin is split open during injury, the body starts to grow epithelial tissue over the open wound at the rate of approximately 1 millimeter every 24 hours. Special collagen-producing cells called fibroblasts rush to the wounded area and start putting down a layer of collagen to strengthen the skin. Normally, these fibroblasts are arranged in an organized fashion. But in emergency repair situations, the collagen is more likely to be laid down haphazardly, resulting in a scar.

But if skin cells are constantly regenerating and dead skin falling off the body, why don't scars eventually soften and blend in with the surrounding skin? Well, skin regeneration works from the bottom up of the epidermis -- the most outer layer of skin. When cells divide, they push up toward the top of the skin, forcing the older layers of skin out. The new cells' DNA carries the same genetic characteristics from one generation of cells to the other. If the characteristics are of scar tissue, that's what gets passed along, and the scarred looking skin remains.

Injuries to the tissue layers below the epidermis are more likely to produce permanent scars than minor injuries to epidermis alone. Ways to reduce scarring include keeping scar tissue moist rather than letting it dry out and avoid picking off scabs.

Resources:

The MSNBC news "Mysteries of the Universe" feature provides more detail about the skin's healing process.