Stretch Marks: Causes, Treatment, and Prevention

Stretch marks, known as "striae" in dermatology circles, are a certain type of dermatological scarring that takes the form of parallel lines. Stretch marks are caused by the scarring of the skin's middle layer, or "dermis", and take the appearance of thin reddish or purplish hued lines, which may fade over time into silver or white lines, but are usually permanent unless removed surgically.

In the simplest terms, skin that is subjected to a greater stretching force than it can manage will tear. Many factors influence the skin's inherent capacity to withstand these stretching forces, including genetics, hormonal changes. There is also a potential link between diet and exercise and skin's resilience, but more research needs to be performed in order to forge a more conclusive link.

There is a hormonal link to the appearance of stretch marks: glucocortoid hormones, steroid hormones produced in the adrenal glands in response to stress and which are part of the body's immune feedback system, have been shown to prevent fibroblasts in the dermis from forming the fibers necessary to maintain a taut appearance of rapidly growing skin, the collagen and elastin. If the skin stretches without this network of supportive fibers, multi-layer tearing occurs, which results in stretch marks. Although this skin stretching plays a major role in the subsequent appearance of stretch marks, it is by no means their sole cause, playing a larger role in determining placement and directionality of stretch marks.

The role of hormones in the formation of stretch marks is further reinforced by the fact that their appearance can be traced to periods of great hormonal change such as puberty, pregnancy, and hormone replacement therapy. Also, bodybuilders may have a higher susceptibility to developing stretch marks, as they experience periods of rapid muscle growth and expansion, which stretches the skin.

Statistics have shown that between seventy-five and eighty percent of pregnant women notice the appearance of stretch marks, primarily in the third trimester, due to the combination of a constant high hormonal level as well as the higher levels of stretching forces. In the pregnancy population, several factors can be examined to determine propensity to develop stretch marks. Women of low maternal age (especially teenagers), who begin their pregnancies with a high body mass index and who have a weight gain over the duration of their pregnancy that is greater than thirty-three pounds have been shown to be at the most risk to develop stretch marks.

Though they make their appearance on the skin'ssurface as a series of red or purple streaks, stretch marks actually originate in the middle layer of the skin, known as the dermis. This resilient supporting layer functions to aid the skin in retaining its shape. When stretch marks appear, the areas affected have an soft, almost empty appearance, which signifies a lack of underlying support. As long as the dermis is supoorted, stretch marks will not form.

The appearance of stretch marks can occur anywhere the integrity of the support layer of the dermis is compromised, but are seen most commonly in areas of the body where there are significant fat deposits. The most common areas that are normally affected are therefore the abdomen (particularly near the naval) breasts, portions of the arms including the upper region and the underarm region, the back, inner and outer thighs, and the hips and buttocks. Though considered by many to be unsightly, they are not a health risk, and they in no way hinder the body's natural ability to heal and repair itself.

Because internal factors such as hormone production and genetics play such a large role in determining one's propensity to develop stretch marks, it is debatable as to whether any form of external treatment can be relied upon to wholly prevent the appearance of stretch marks. Certain extra rich emollients such as cocoa butter have been suggested as limited efficacey means for preventing stretch marks, but their main function seems to be quelling the itchiness that is associated with stretch marks. Most treatments focus on the complete or partial erasure of existing marks, and have therefore a much higher success rate. Examples of these treatments would be Revitagen-Fx, StriVectin-SD, and Trilastin, among others.