Why do some scars never disappear even though the skin renews itself ?

 

When it suffers small injuries, the skin has a remarkable capacity for regeneration. In a few days, it is able to renew its cells to restore the integrity of the skin barrier. But sometimes, certain injuries cause scars that remain visible for life. How to explain this phenomenon ?

The healing process

To heal after an injury, the skin goes through several phases. Inflammation occurs first, as soon as the skin barrier is damaged. It is characterized by swelling of the affected area, redness, heat and the perception of pain. Inflammation helps cause immune cells to flock to the injury to clear out microbes and debris.

Next comes the proliferation phase. Certain specialized cells, such as fibroblasts, produce proteins and collagen to promote the formation of new skin tissue. Blood vessels appear to nourish this growing tissue.

Eventually, during the maturation phase, which sometimes lasts months or even years, the scar tissue is remodeled to make the skin more resilient.

Factors that influence the quality of healing

Healing and its effectiveness are mainly based on three criteria. The organization of collagen plays a crucial role in the appearance of the scar. If these proteins are arranged in a disorganized way, they affect the texture and elasticity of the injured area.

On the other hand, the formation of lasting scars can occur when the repaired tissue differs from the original tissue, and is less functional or has aesthetic disparities. For example, the absence of hair and oil glands on scar tissue makes it different from the rest of the skin.

Finally, the duration and intensity of the inflammatory response influence the formation of so-called hypertrophic or keloid scars. The former are often red, thick and raised, resulting from excessive collagen production during healing. Keloid scars are more severe than hypertrophic scars and sometimes extend beyond the initially injured area. They result from an abnormal proliferation of fibrous tissue.

It should also be considered that when underlying tissue is lost as in the case of severe acne, holes form under the skin, which lead to long-lasting scars called atrophic.

Other factors that affect healing

The location of the injury can affect the quality of healing. The face, well irrigated, generally heals well, while the back and shoulders are more conducive to the formation of raised scars. Deeper or more extensive wounds involve a more complex healing process, with a higher risk of developing into a visible scar.

With age, the skin also tends to regenerate more difficult, which can encourage the formation of permanent scars.