Stretch marks

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.[6]

Stretch marks occur in the dermis, the resilient middle tissue layer that helps the skin retain its shape. 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 body's ability to function normally and repair itself, however, they are often considered a cosmetic nuisance.[7] Young women are generally affected the most and often seek treatment for them from a dermatologist[8] and following pregnancy.[9]

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  Striae gravidarum in a pregnant woman at 38 weeks
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  Stretch marks from pregnancy >1 year postpartum
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  Normal stretch marks in a teenage male
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  Stretch marks in a female breast
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  Striae distensae on an obese male

Stretch marks appear to be caused by stretching of the skin. This is especially true when there is an increase in cortisone[10] – an increase in cortisone levels can increase the probability or severity of stretch marks by reducing the skin's 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. This is particularly the case when there is new tissue growth (which can interfere with the underlying physical support of the dermis or epidermis, by displacing the supportive tissue).

Examples of cases where stretch marks are common, also given by the Mayo Clinic, include weight gain (in the form of fat and/or muscle), pregnancy, and adolescent growth spurts, though it is also noted that some medications, as well as other medical conditions and diseases, may increase the likelihood of stretch marks appearing. In the case of medication, the Clinic points to "corticosteroid creams, lotions and pills and chronic use of oral or systemic steroids" as a common contributing factor. Medical conditions that can contribute to stretch marks include Ehlers-Danlos syndrome, Cushing's syndrome, Marfan syndrome, and "adrenal gland diseases".[11][12][13]

Collagen and elastin are proteins in the skin that contribute to the skin's strength, resilience, flexibility, and help skin that has been stretched to recover its original state. Boosting the production of collagen and elastin helps prevent stretch marks from occurring.[20] Stretch marks can also derive from nutritional deficiencies. Consuming foods that contribute to the skin's health, such as zinc-rich foods, foods high in vitamin A, C, D, and protein rich foods, can help suppress stretch marks.[21] A systematic review has not found evidence that creams and oils are useful for preventing or reducing stretch marks in pregnancy.[4] The safety in pregnancy of one ingredient, Centella asiatica, has been questioned.[18] Evidence on treatments for reducing the appearance of the scars after pregnancy is limited.[18]

There are no clearly useful treatments for stretch marks, although there are many different suggestions on how to remove them or lessen their appearance.[5]

Various efforts that have been tried including laser treatments, glycolic acid, and microdermabrasion.[22] Tretinoin (0.1% w/w), which is a retinoid, has found to be effective on early stretch marks in several studies. Hyaluronic acid also improves the appearance of stretch marks.[23][24] Topical tretinoin is categorized by the FDA as a known teratogen (causing malformations in fetuses) in animals, without adequate human studies on safety in pregnancy.[25]

Carboxytherapy is a known procedure; however, there is a lack of evidence to support how effective it is.[26]

Research into a new skin grafting technique called "microcolumn grafting / micrografting," that uses needles to take autologous full-thickness skin biopsies, is also being looked into as a potential treatment for stretch marks.[27][28]

Since ancient times, pregnant women have sought remedies to prevent stretch marks during pregnancy. Both ancient Greeks and Romans used olive oil, while Ethiopians and Somalis used frankincense.[29]

Striae were first recognized by Roederer in 1773, and were later histologically described by Troisier and Ménétrier in 1889.[30] In 1936, Nardelli made the first morphologically correct descriptions.[31]

Medical terminology for these kinds of markings includes striae atrophicae, vergetures, stria distensae, striae cutis distensae, lineae atrophicae, linea albicante, or simply striae.