Stretch marks, or striae, are a type of skin scarring that affects the dermis and epidermis layers of the human skin. There is really only one type, but they can be categorized in a number of different ways. First appearing as red or purple lines on the skin, the scars usually fade to silver-pink or white within a few years. Experts believe that they develop for two different reasons: when the tissue beneath the skin grows faster than the skin itself or because of hormones. They are more likely to develop during pregnancy, adolescence and when a person is undergoing physical training. Although many treatments, such as topical oils and laser resurfacing, are available, none have proven consistently effective at preventing, reducing or removing the scars.
How Stretch Marks Form
The science behind different types of stretch marks is not definitive, and there are two major theories are in place for why they happen. The first has to do with rapid expansion of the skin, while the second relates to hormones.
The human skin is made up of three layers: the epidermis, the dermis, and the subcutis. The middle layer, the dermis, is rich in collagen, which is meant to keep the skin taut. The theory that is most widely accepted about stretch mark formation is that, in any period of rapid growth, collagen production isn't always able to keep up with the stretching of skin. The dermis sometimes tears and loses elasticity, resulting in discolored scarring of the skin, or a stretch mark.
While the stretching-skin theory is commonly accepted, some experts argue that a hormone called glucocorticoids is responsible. The body secretes this hormone in high concentration in adolescents, pregnant women, bodybuilders and those suffering from obesity. Experts suggest that the hormone prevents collagen from forming, causing a breakdown in elasticity. While the stretch marks may appear in areas subject to sudden growth, it is possible that the scarring is caused by the hormone increase, rather than the growth itself.
Types by Coloration
A simple way to classify stretch marks regardless of their origin or location is by color. Red or purple stretch marks are fairly new, typically less than a year old. Ones that are older than a year usually appear as silvery or white. Dermatologists usually consider red or purple stretch marks easier to treat, because the skin is still in the process of trying to heal.
Types by Cause
In adolescence, growth spurts or sudden weight gain can cause stretch marks. Most commonly, they occur where fat is stored, and typical areas for growth-spurt related types of stretch marks are the back, upper arms, breasts, hips and thighs. Some studies have shown that as many as 70% of adolescent girls and 40% of adolescent boys are affected by striae.
Bodybuilding or weightlifting can lead to stretch marks. In these cases, marks usually appear on the growing muscles, such as the biceps or calves. Users of steroids, such as cortisone, are particularly subject to these types of stretch marks. Steroid use lets a person rapidly build muscle tissue, which might cause skin to stretch at an increased rate.
One of the most common groups affected by stretch marks is women who are pregnant. As the unborn baby grows, it rapidly expands in the uterus, stretching the skin over the abdomen. The breasts also get bigger in preparation for breastfeeding.
Studies suggest that between 70 and 90% of pregnant women develop stretch marks. Most medical professionals and women see them as a completely normal part of pregnancy, although most women still are not happy to get them. They usually show up around the third trimester, or around the seventh month of pregnancy. Prior to this point, the baby usually isn't big enough to cause extreme stretching of the skin tissue.
Removal Methods and Their Effectiveness
Most types of stretch marks usually fade with time, but they are unlikely to disappear entirely. Companies and some people in the medical field sometimes recommend various topical oils and creams to prevent stretch marks from appearing, with mixed results. People also turn to laser treatments, chemical peels and ointments to reduce the appearance of already formed striae. The idea with these methods is that they keep the skin supple, encouraging healthy skin cell turnover and stimulating collagen growth so that the scar tissue eventually goes away.
Despite plenty of hype, most physicians acknowledge that the majority of creams, oils and resurfacing techniques recommended for stretch marks are ineffective. Much of this is because they do not penetrate to the deeper layers of the skin where the stretch marks actually are. No treatment has been proven to completely remove the striae.