How does a scar develop?
A fall, a bite, a burn or surgery: skin injuries can leave scars. These occur as part of the wound healing process: the skin damaged or destroyed by the injury is replaced by less elastic scar tissue.
However, not every wound will result in a scar. For example, if only the upper layers of the epidermis are injured, but the basal layer – the lowest layer of the epidermis – is intact, new skin tissue can be formed starting from there (regenerative wound healing).
Reparative wound healing leaves scars
However, if the second layer of skin (dermis) is damaged in addition to the epidermis, this type of repair no longer works. The body must “patch” the injured skin with connective tissue (reparative wound healing): New, not very stable tissue (called granulation tissue) forms from the wound edges, which the body fills with collagen. This is a fibrous protein involved in the formation of connective tissue (skin, ligaments, tendons).
Because of the increased blood supply, this fresh scar looks red. It is also somewhat raised compared to the surrounding healthy skin. If the blood supply decreases, which may be the case after months or even years, the collagen contracts – the scar becomes flatter, paler and softer.
Scar tissue does not correspond exactly to the destroyed skin tissue, but is different. Compared to the surrounding skin, it is usually less elastic, has neither sweat nor sebaceous glands and also no sensory cells. Similarly, scar tissue lacks pigment-forming cells (melanocytes) that are normally found in the epidermis and provide for tanning of the skin when exposed to sunlight.
Some scars are clearly visible for a lifetime, while others (almost) disappear with time.
Types of scars
Scars can look very different – depending, among other things, on how they were formed. In addition to the conventional, usually symptom-free scarring with pale, flat, white skin overgrowth, medical experts distinguish between four pathological scar types:
Atrophic scars.
This type of scar is sunken. This is because too little scar tissue has formed, so that it does not completely fill the wound. Atrophic scars, or scar depressions, often occur after severe acne, for example.
Hypertrophic scars
These raised, thickened and often itchy scars occur when an excessive amount of scar tissue forms – but limited to the wound area. This often happens after burns or at flexion points (e.g. knee, elbow), where high traction forces prevail due to movement. Sometimes these scars regress on their own.
Keloids
Read more about this form of pathological scars in the article Keloid.
Scar contractures
They occur when scar tissue contracts and hardens severely. Such hardened scars can restrict mobility, especially if they are located in the area of joints. Scar contractures often form after burns, wound infections and extensive injuries.
Removing scars
Even though scars are usually harmless and rarely proliferate, many affected persons perceive large and/or red scars in particular as an aesthetic blemish and suffer accordingly. The good news: The healing process can be supported by own and medical measures.
Very conspicuous or pathological scars, where too little or too much scar tissue is formed, can be removed by the doctor in various ways. This is done, for example, by means of icing, abrasion, lasers or surgery.
You can read more about the different methods in the article Removing scars.
Scar care
A scar usually cannot be made completely invisible. However, there are ways to make them more inconspicuous and the tissue more supple. For example, scars do not like the sun, cold or friction. On the other hand, massages and regular application of cream are good for the scar tissue.
You can read more about this topic in the article Scar Care.
Scars: course and prognosis
Due to the lack of sebaceous and sweat glands as well as the often reduced sensitivity in the scar area, affected persons may not sweat at the scar site or report numbness.
In the case of very large scars or scars in areas that are frequently exposed to movement, mobility may be restricted. This is because the scar tissue is less elastic than the surrounding skin. If it is subjected to tension during movement, this can be uncomfortable or even painful.
In addition, scar pain can also occur with an inflamed scar.