Scar tissue is not identical to the tissue that it replaces and is usually of inferior functional quality. For example, scars in the skin are less resistant to ultraviolet radiation, and sweat glands and hair follicles do not grow back within scar tissue. A myocardial infarction, commonly known as a heart attack, causes scar formation in the heart muscle, which leads to loss of muscular power and possibly heart failure. However, there are some tissues (e.g. bone) that can heal without any structural or functional deterioration.
The word scar was derived from the Greek word eschara, meaning place of fire (fireplace).
A scar is a natural part of the healing process. Skin scars occur when the deep, thick layer of skin (the dermis) is damaged. The worse the damage is, the worse the scar will be.
Most skin scars are flat, pale and leave a trace of the original injury that caused them. The redness that often follows an injury to the skin is not a scar, and is generally not permanent. The time it takes for it to go away may, however, range from a few days to, in some serious and rare cases, a few years. Various treatments can speed up the process in serious cases.
Scars form differently based on the location of the injury on the body and the age of the person who was injured.
To mend the damage, the body has to lay down new collagen fibres (a naturally occurring protein that is produced by the body). Recent research has implicated the gene osteopontin in scarring and developed a gel that inhibits the process .
This process results in a fortuna scar. Because the body cannot re-build the tissue exactly as it was, the new scar tissue will have a different texture and quality than the surrounding normal tissue. An injury does not become a scar until the wound has completely healed.
Transforming Growth Factors (TGF) play a critical role in scar development and current research is investigating the manipulation of these TGFs for drug development to prevent scarring from the emergency adult wound healing process. As well, a recent American study implicated the protein Ribosomal s6 kinase (RSK) in the formation of scar tissue and found that the introduction of a chemical to counteract RSK could halt the formation of Cirrhosis. This treatment also has the potential to reduce or even prevent altogether other types of scarring.
Keloid scars can occur on anyone, but they are most common in dark-skinned people. Keloid scars can be caused by surgery, an accident, by acne or, sometimes, from body piercings. In some people, keloid scars form spontaneously.
Although they can be a cosmetic problem, keloid scars are only inert masses of collagen and therefore completely harmless and non-contagious. However, they can be itchy or painful in some individuals. They tend to be most common on the shoulders and chest.
Alternately, a scar can take the form of a sunken recess in the skin, which has a pitted appearance. These are caused when underlying structures supporting the skin, such as fat or muscle, are lost. This type of scarring is commonly associated with acne, but can be caused by chickenpox, surgery or an accident.
Scars can also take the form of stretched skin. These are called striae and are caused when the skin is stretched rapidly (for instance during pregnancy, significant weight gain or adolescent growth spurts), or when skin is put under tension during the healing process, (usually near joints). This type of scar usually improves in appearance after a few years.
In historical sequence, corticosteroid therapy by injection into the scars was introduced in the 1960s, from the early 1970s pressure garment therapy was introduced for widespread burn scars, and silicone gel sheets from the 1980s.
Pressure garments are usually custom-made from elastic materials, and fit tightly around the scarring. They work best when they are worn 24 hours a day for six to twelve months.
It is believed that they work by applying constant pressure to surface blood vessels and eventually causing scars to flatten and become softer.
The steroid is injected into the scar itself; since very little is absorbed into the blood stream, side effects of this treatment are minor. This treatment is repeated at 4-6 week intervals.
Vascular lasers have been proven to greatly reduce the redness of most scars 6-10 weeks after the initial treatment. They have not been proven effective in flattening scars however. It has been theorized that removing layers of skin with a carbon dioxide or erbium laser may help flatten scars.