They are caused by tearing of the dermis, and over time can diminish but not disappear completely. Stretch marks are generally associated with pregnancy and obesity. Stretch marks are the result of the rapid stretching of the skin associated with rapid growth (e.g. puberty) or weight gain (e.g. pregnancy), and anabolic steroid use. Although the skin is fairly elastic, rapid stretching of the skin will leave permanent stretch marks.
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