No stretch marks will form as long as there is support within the dermis; stretching plays a role in where the marks occur and in what direction they run, however, there are a number of contributing factors (see: "Causes", below) to their formation.They can (but do not always) cause a burning and itching sensation, as well as emotional distress. They pose no health risk in and of themselves, and do not compromise the bodys ability to function normally and repair itself, however, they are often considered a cosmetic nuisance. Young women are generally affected the most and often seek treatment for them from a dermatologist and following pregnancy. Causes
Stretch marks appear to be caused by stretching of the skin. This is especially true when there is an increase in cortisone –  an increase in cortisone levels can increase the probability or severity of stretch marks by reducing the skins pliability. More specifically, it affects the dermis by preventing the fibroblasts from forming collagen and elastin fibers necessary to keep rapidly growing skin taut; this can create a lack of supportive material as the skin is stretched, and lead to dermal and epidermal tearing, which in turn can produce scarring in the form of stretch marks.
Stretch marks, also known as striae () or striae distensae, are a form of scarring on the skin with an off-color hue. Over time they may diminish, but will not disappear completely. Striae are caused by tearing of the dermis during periods of rapid growth of the body, such as during puberty or pregnancy, in which they usually form during the last trimester. Usually on the stomach, these striae also commonly occur on the breasts, thighs, hips, lower back, and buttocks. Pregnancy-related striae are known as striae gravidarum. Striae may also be influenced by the hormonal changes associated with puberty, pregnancy, bodybuilding, or hormone replacement therapy. There is no evidence that creams used during pregnancy prevent stretch marks. Once they have formed there is no clearly effective treatment, though various methods have been attempted and studied. Signs and symptoms
Striae, or "stretch marks", begin as reddish or purple lesions, which can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored; the most common places are the abdomen (especially near the navel), breasts, upper arms, underarms, back, thighs (both inner and outer), hips, and buttocks. Over time, they tend to atrophy and lose pigmentation. The affected areas appear empty, and are soft to the touch.Stretch marks occur in the dermis, the resilient middle tissue layer that helps the skin retain its shape.