Scarring and the Skin Healing Mechanisms

The removal or fading of scars, lesions, and stretch marks from the skin depends on a process called "skin remodeling".

The skin is designed to repair wounds rapidly to avoid blood loss and infections. Scars are created from a rapidly formed "collagen glue" that the body brings into an injured area for protection and strength. In ideal skin repairing, damaged skin is rapidly closed, and then the healed area is slowly repaired to remove the remaining collagen scars and blend the skin area into nearby skin.

Scar collagen is removed and replaced with a mixture of skin cells and invisible collagen fibers. This remodeling may continue in a skin area for up to ten years.

In children, the remodeling speed is high and scars are often rapidly removed from injured skin areas. But as we become adults, this rate diminishes and small scars may stay there for years.

One way to quicken repair is to make a small amount of controlled skin damage with a needle, laser, acid, or other means, and then let the body repair processes reconstruct the skin area.

A second method is to use enzymes and fibroblast proliferators to increase the body's natural rebuilding mechanisms and achieve even better final results. Fibroblasts are the cells in the basal membrane of the skin and they are the precursors of all the structural elements of healthy skin, including those that provide moisture, tensile strength and elasticity to skin. Enzymes dissolve or "digest" damaged and dying cells.

Wound Healing

Scars are always needed to reconnect skin that has been damaged. Initially, they may be red or dark and pink after the wound has been healed but will become softer and flatter naturally over time, resulting in a flat, pale scar.

For reasons that are still waiting to be fully understood, some people form raised scars that are red and thick and may cause itch or pain. Others develop scars that grow beyond the site of an injury, called keloid scars.

Keloid scars are actually thick, puckered, itchy clusters of scar tissue that grow beyond the edges of an injury or incision and rarely regress. They appear when the body keeps producing tough, fibrous protein (known as collagen) after a wound has healed.

Keloids can result from any type of injury to the skin, including scratches, injections, insect bites, tattoos or medical procedures. Keloids can appear anywhere on the body, but most commonly occur over the breastbone, on earlobes and on shoulders.

Keloids are fibrotic tumors characterized by a collection of atypical fibroblasts with high deposition of extracellular matrix components, especially collagen, fibronectin, elastin, and proteoglycans. Histologically, keloids contain relatively acellular centers and thick, abundant collagen bundles that form nodules in the deep dermal portion of the lesion. Keloids present a clinical challenge that must be addressed as these lesions can cause significant pain, pruritus (itch) and physical disfigurement, may not improve its appearance over time, and can even limit mobility if located over a joint.

Hypertrophic scars sometimes are hard to distinguish from keloid scars histologically and biochemically, but unlike keloids, hypertropic scars are confined to the wounded site and use to mature and flatten out over time. Both types produce larger amounts of collagen than normal scars, but often the hypertrophic type shows declining collagen synthesis after about 24 weeks. Hypertrophic scars contain nearly twice as much glycosaminoglycans as normal scars, and this and enhanced synthetic and enzymatic reactions result in important alterations in the matrix which affects the mechanical properties of the scars, including decreased extensibility that makes them feel firm.

As with hypertrophic scarring, people who have developed one keloid scar are likely to be prone to this condition in the future and should speak with their doctor or surgeon if they are likely to need injections or to have any kind of surgery.

Atrophic scars are characterized by a thinning and diminished elasticity of the skin due to a loss of normal skin architecture. An example of an atrophic scar is striae distensae, also known as stretch marks.