Stretch marks are long, narrow streaks, stripes or lines that develop on the skin and which differ in hue from the surrounding skin. They are the result of a sudden stretching of the skin and are extremely common. Anyone can develop stretch marks, although they tend to affect more women than men.
Stretch marks can be visible on body parts including the tummy, thighs, hips, breasts, upper arms, and lower back. The marks form in the middle layer of the skin; when there is a constant stretch, the layer tears, leaving stretch marks.
This type of scarring happens when the skin cannot bounce back after a period of intense growth, be that due to pregnancy, weight gain, or during puberty. Extreme weight loss can also make stretch marks more visible, and some stretch marks arise as a result of acute trauma affecting the skin (such as a car accident when heavily pregnant).
Stretch marks are usually a slightly red or purple shade to begin with, fading with time to silvery white lines that may or may not disappear.
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You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on stretch marks
Here are some key points about stretch marks. More detail and supporting information is in the main article.
- The prevalence of stretch marks ranges from 40-90%, depending on race, age and sex.
- Both sexes are affected by stretch marks.
- Around 70% of girls develop stretch marks during puberty.
- Around 40% of boys develop stretch marks during puberty.
- Stretch marks can occur during pregnancy, puberty, after rapid weight gain, during various medical conditions and after using certain medications.
- Stretch marks often appear after the 25th week of pregnancy.
- Common areas for stretch marks to arise include the abdomen, breasts, hips, flank, buttocks and thighs.
- Stretch marks are more common in younger pregnant women.
- Cocoa butter is not effective in preventing stretch marks.
- Laser therapy has proven effective for stretch mark removal.
What are stretch marks?
Stretch marks are also called striae distensae, SD, striae, striae atrophicans and striae gravidarum. They are dermal scars or disfiguring lesions characterized by flattening and atrophy (wasting or degeneration) of the epidermis (the outermost layer of the skin).1,47
Stretch marks are linear, smooth bands on the skin that, depending on skin color, can appear as red or purple and which fade over time to leave silvery pale marks.3,10,34
Stretch marks are long, narrow streaks that are visible on the surface of the skin as a result of sudden stretching of the skin.
Occurring in 40-90% of women, stretch marks appear following rapid repeated over-stretching of the skin over weak connective tissue. The most common areas affected are the:10,46,48,49,55
Skin changes are common in pregnancy with stretch marks occurring in over 70% of pregnant women, usually after 25 weeks of gestation.25
Stretch marks are not medically dangerous, but can be a cause of aesthetic concern and anxiety. For some people, stretch marks are such a significant cosmetic concern that they affect quality of life.10 They can be disfiguring, causing emotional and psychological distress, especially during puberty, the latter stages of pregnancy (when they are most prominent), in the postnatal period where they appear pale, or after significant weight loss.33,40,51
This type of dermatological scarring is particularly challenging and tends to occur with:47,3
- Rapid weight gain
- Numerous medical conditions
- Certain therapeutic interventions.
Stretch marks are common during the later stages of pregnancy; their occurrence depends largely on skin type and skin elasticity.
Preliminary research in women undergoing a second Caesarian section has revealed that the greater the severity of stretch marks in pregnancy the more likely it is that intraperitoneal adhesions are present, which may complicate the second C-section or other abdominal surgery.
Intraperitoneal adhesions were present in half of those with severe striae gravidarum, 30% of those with mild stretch marks, and fewer than 1 in 10 (9.1%) of those with no stretch marks.63
Hormones are produced during pregnancy that soften pelvic ligaments and increase their flexibility. Hormones also soften skin fibers, giving an increased risk of stretch marks.
Stretch marks appear on the abdomen as the baby grows and sometimes occur in the skin covering the thighs and breasts.
The body goes through rapid growth cycles during puberty which can cause the development of stretch marks. In males, stretch marks commonly arise on the shoulders and back, while females typically develop stretch marks on the hips, thighs and breasts.
Rapid weight gain
Stretch marks may also arise if a person gains weight rapidly, such as when bodybuilders and athletes dramatically increase muscle mass over a short period of time.
Medical conditions such as Cushing's syndrome and Marfan syndrome can lead to the development of stretch marks. Marfan syndrome is a genetic condition that causes weakness and decreased elasticity in body tissues.
Cushing's syndrome can cause stretch marks because the condition involves the overproduction of cortisol (the stress hormone), which can lead to rapid weight gain, especially in the abdomen, in addition to causing the skin to become fragile, thin and more susceptible to bruises, scarring and infection. Cushing's syndrome is three times more common in women than in men, but can be successfully treated in most cases.
Ehlers-Danlos syndrome (EDS) is a rare inherited condition that disrupts the integrity of structural proteins in the skin which can also cause stretch marks.
Late-stage faded stretch marks are a type of scar characterized by a loss of collagen. This key structural protein is found throughout the body, providing strength and cushioning to many different areas, including the skin - and elastic fibers in the dermis. The dermis is the sensitive layer of skin below the epidermis, containing nerve endings, sweat and sebaceous glands, and blood and lymph vessels.38
What causes stretch marks?
The skin consists of three key layers: epidermis (the outer layer), dermis (the middle layer) and subcutaneous or hypodermis (the deepest layer). Stretch marks form in the dermis when the connective tissue is "stretched" beyond the limits of its elasticity due to rapid expansion or contraction of the skin from sudden growth or weight gain.
The three main layers of the skin are the epidermis, dermis and hypodermis. Stretch marks are caused when the dermis is stretched so rapidly it tears.
The abrupt stretching causes the dermis to tear which allows deeper skin layers to show through, forming the stretch marks.
Usually, as the body grows, the strong connecting fibers in the dermis slowly stretch. However, with rapid growth, the fibers overstretch and break. Stretch marks are red or purple initially due to blood vessels showing through the tears in the dermis.
Stretch marks eventually fade to a silvery, white or glossy appearance due to the blood vessels contracting and the pale fat underneath the skin becoming visible instead.
Stretch marks are more likely to develop and to appear more extreme where there are high levels of circulating cortisone, or where cortisone is used topically. Cortisol, the stress hormone produced by the adrenal glands is converted into cortisone, which weakens elastic fibers in the skin.57
A number of risk factors have been associated with the development of stretch marks but the evidence supporting these associations is highly variable. Much remains to be understood about the etiology, diagnosis and treatment of stretch marks.33,47
The pathogenesis of stretch marks is unknown but is likely to relate to changes in the fibroblast phenotype.3
A study that compared skin biopsies from volunteers with normal skin (NS), and both stretch-mark skin (SM) and normal-looking skin (NL) from patients with stretch marks found that:2
- There was less DNA, protein, and elastin in the skin of people with stretch marks compared to the skin of those without stretch marks, with those deficiencies more profound in SM skin.
- Cells derived from NL and SM skin had slower than normal outgrowth of their fibroblasts, demonstrating low migration and proliferation rates, and producing less elastin, fibrillin 1, collagen 1, and fibronectin than cells derived from NS.
The skin structure of stretch marks is qualitatively and quantitatively different compared to healthy skin. The altered appearance of the skin reflects structural modifications in the dermis.48
A series of tests led to the discovery of a dormant phenotype in dermal fibroblasts from patients with stretch marks. These tests may help predict a predisposition to stretch marks and could open up a new approach for preventive treatments for people predisposed to stretch mark formation.2
The cause and associated factors for stretch mark occurrence could be linked to:14,17,21,30,33,39,53,54
It has been shown that women with a higher BMI have an increased risk of stretch marks.
- Maternal age
- Hormone changes
- Genetic factors
- Inherited defects
- Pre-pregnancy BMI
- Maternal BMI at delivery
- Gestational age at delivery
- Birth weight of the baby
- Alcohol consumption
- Water intake
- Family history
- Physical stretching of the skin.
Women with a higher body mass index (BMI) have more stretch marks, except in cases where stretch marks are related to breast augmentation, in which case a low or normal BMI increases the likelihood of stretch marks.62 They are more frequently observed in younger women, with teenagers suffering the most severe stretch marks.
These findings may be explained by the greater degrees of stretch applied to the skin in obese women with larger babies, and by changes in skin collagen and connective tissue that are age-related and which affect its likelihood of tearing.33,56
One study suggests that increased maternal age could be a protecting factor against stretch marks during pregnancy.21
It has been suggested that genetics may play a role in the development of stretch marks. Regardless of the etiology, all stretch marks display the same changes in the dermis, showing atrophy and loss of rete ridges (rete ridges are the downward projections of the epidermis that interlock with the papillary or superficial dermis). These findings are similar to those seen with scar formation.55
Research has also indicated that areas of skin that undergo greater mechanical stretching may respond differently to hormonal signals from estrogens, androgens and glucocorticoids. This is because under such conditions the skin cells appear to express greater hormonal receptor activity. In fact, in one small study involving eight people with stretch marks and eight without, estrogen receptors were twice as concentrated in the skin of those with stretch marks.39
Recent developments on causes of stretch marks from MNT news
The symptoms of Cushing disease are unmistakable to those who suffer from it - excessive weight gain, acne, distinct colored stretch marks on the abdomen, thighs and armpits, and a lump, or fat deposit, on the back of the neck. Yet the disorder often goes misdiagnosed.
23andMe, the leading personal genetics company, has conducted the first genetic study of striae distensae (stretch marks). Researchers at the company identified four genetic markers significantly associated with the development of stretch marks that inform why some individuals are more susceptible to the skin condition.
Signs and symptoms
Before stretch marks begin to emerge, the skin can appear thin and pink and may feel irritated or itchy.
The marks initially develop as wrinkly, raised streaks that can be red, purple, pink, reddish-brown or dark brown, depending on skin color. The streaks eventually fade, flatten and change to a silvery color over time, becoming less noticeable (this can take years).
Tests and diagnosis
Stretch marks are easily diagnosed based on a skin examination and review of medical history. The doctor will usually ask questions based on signs and symptoms, any medications currently being used and any existing medical conditions.58
Stretch marks are not harmful in themselves and do not cause medical problems. In rare cases they may indicate an underlying medical issue that requires treatment or monitoring.
Recent developments on diagnosis of stretch marks from MNT news
Stretch marks are caused by a sudden or excessive stretching of the skin due to pregnancy, rapid weight gain, puberty or other cause such as surgery or trauma. Almost half of all pregnant women develop stretch marks.
Treatment and prevention
Creams, gels, lotions, laser and cosmetic surgery have all been proposed as treatments for stretch marks, although there is little medical evidence to support the efficacy of such treatments.25 Current treatments are particularly limited in their ability to deliver long-lasting improvements for all skin types.37
Often stretch marks fade over time and become unnoticeable. For people who developed stretch marks in pregnancy, these are usually less noticeable 6-12 months after giving birth. Cosmetic camouflage (makeup) can be used to temporarily conceal marks.
Advances in laser technologies and ongoing research mean that the future looks bright for developing effective treatments for stretch marks.26
Creams, oils, topical preparations
Several studies have found little or no statistically significant difference in the development of stretch marks when comparing topical preparations (something applied to the surface of the body) that include active ingredients with a placebo (preparations without active ingredients) or with no treatment.
There is no high-quality evidence to support the use of topical preparations in the prevention of stretch marks during pregnancy.9,10,43
The majority of creams, oils and lotions do not seem to reduce the likelihood of stretch marks occurring.
Creams and oils do, however, help with skin dryness and may reduce itching.
Six studies involving 800 participants found no statistically significant average differences in the development of stretch marks with the use of preparations such as Alphastria, Trofolastin, Verum, olive oil and cocoa butter, all of which contain vitamin E (Alphastria and Verum also contain hyaluronic acid).43
One study evaluated the use of an anti-stretch mark cream containing hydroxyprolisilane-C, rosehip oil, Centella asiatica triterpenes and vitamin E, which proved to be effective in reducing the severity of the stretch marks during pregnancy, preventing the appearance of new stretch marks and halting progression of those already present. In women with no stretch marks, use of the anti-stretch mark cream was more effective than placebo in preventing new stretch marks.45
In studies of 300 and 175 women, application of a lotion containing cocoa butter did not appear to reduce the likelihood of developing stretch marks during pregnancy.27,52
Bitter almond oil
A study aiming to identify the effect of applying bitter almond oil with and without massage for preventing stretch marks during pregnancy found that a 15-minute massage applied with almond oil during pregnancy reduced the development of stretch marks.
Applying bitter almond oil without massage had no apparent effect, however, leading the authors of this study to conclude that those who are pregnant should be informed of the positive effects of massaging with applied almond oil early in pregnancy.40,51
Studies looking at the effects of olive oil on stretch marks occurring in the second trimester of pregnancy found the treatment ineffective in reducing the occurrence or severity of stretch marks.36,52
Olive oil has not been shown to significantly reduce stretch marks and is not recommended for stretch mark prevention.
Another study comparing 50 women applying topical olive oil twice a day with a control group applying none, showed that although olive oil reduced the frequency with which severe stretch marks developed, it did not significantly reduce the overall incidence and severity of stretch marks and could not be recommended for stretch mark prevention.41
Tretinoin cream (retinoic acid)
Products containing retinoic acid are teratogenic (can result in congenital defects) and should not be used by anyone who is pregnant or breastfeeding.61
Tretinoin is extensively used in the treatment of acne (as Retin-A) and in the treatment of stretch marks.12,13
Studies indicate that the topical application of tretinoin significantly improves the clinical appearance of early stretch marks, although the process responsible for the clinical improvement is unknown.15,20
In one study, tretinoin reduced the length of the stretch marks by 14% and the width by 8% after six months of treatment. 65 In another study, 12-weeks of treatment decreased the length of stretch marks by 20%.64
Note that products containing retinoic acid should not be used if pregnant or nursing.61
Tretinoin helps to rebuild collagen, which makes stretch marks look more like "normal" skin.59
A study of 20 volunteers who massaged silicone and placebo gels into separate sides of the abdomen daily for 6 weeks showed that the application of silicone gel increased collagen levels and reduced pigmentation compared with a placebo. These findings could provide preliminary evidence of the use of topical gels in the clinical management of stretch marks.42
Microdermabrasion is a popular technique used in the treatment of several skin problems, including acne, acne scarring, stretch marks, and photoaging. The procedure appears to result in an improvement in skin contour irregularities with significant improvement in early stretch marks.22
This treatment involves a device that blows crystals onto the skin, "polishing" the skin's surface while a vacuum tube removes both the crystals and skin cells. The top layer of the skin is gently removed, stimulating growth of new elastic skin.59
Side effects are less frequent with microdermabrasion and patients are more likely to stick with (adhere to) the treatment compared with topical tretinoin.46
The use of lasers to diminish the appearance of stretch marks or in combination with other treatments can provide safe and effective reduction in the appearance of both red (early-onset) and white (late-stage) stretch marks. Many laser therapies require special measures for darker skin types as altered pigmentation can be more challenging in dark skin. 8,31
A doctor can give advice as to which form of laser treatment would be suitable. Laser therapies work by using wavelengths of light to stimulate growth of collagen, elastin or melanin production in the skin.59
For early stretch marks, pulsed dye lasers have been shown to be effective, as has fractional laser treatment for older stretch marks.
Clinical improvements to stretch marks have been obtained with the following devices in studies by potentially stimulating new collagen and elastic fiber synthesis:
- 1,064-nm Nd:YAG laser28
- 1540-nm fractional nonablative laser37
- 1550-nm fractional nonablative laser35
- Fractional CO2 laser38,49
- Fractional photothermolysis25
- Pulsed dye laser6,16,31,50
- Copper bromide laser.5
Other technologies that shown promise in studies of alternative treatments for stretch marks include:
Various medicinal herbs and combinations of botanicals have been claimed to treat stretch marks. There is no evidence that any of these work.
- Intense pulsed light (IPL)7,44,50
- TriPollar radiofrequency device.24
Alternative therapies often claimed to treat stretch marks include plant extracts such as aloe vera, combinations of botanicals, vitamins, tea tree oil, fruit acids, lemon juice, potato juice, egg whites and alfalfa. There is no evidence that these products work.60 There is weak evidence that hyaluronic acid may help prevent stretch marks.66
There is also some evidence that Centella asiatica (gotu kola) can prevent stretch marks; research suggests that gotu kola can promote collagen synthesis and fibroblast proliferation and increase intracellular fibronectin content, helping to improve the tensile strength of newly formed skin while inhibiting inflammation that leads to the developing of hypertrophic scars and keloids.67
It has been demonstrated that ultrasound can diagnose stretch marks; PRIMOS devices can detect and measure stretch mark type and maturation.
A high-frequency ultrasound and 3D image device has also been used successfully to evaluate the effectiveness of a topical treatment for stretch marks.41
Ultimately, stretch marks cannot always be prevented, although these steps may help to reduce the risk:
- Maintain a healthy weight
- Avoid yo-yo dieting
- Eat a balanced diet rich in vitamins and minerals - particularly vitamins A and C and the minerals zinc and silicon for healthy skin
- Aim for slow and gradual weight gain during pregnancy
- Drink plenty of water (6-8 glasses daily).
Recent developments on treatment of stretch marks from MNT news
Merz Pharma Canada announced the availability of Mederma Skin Care for Scars Gel and Mederma Stretch Marks Therapy at retailers nationwide.
Dr. Worophong Manuskiatti was invited to present results of his study "Treatment of striae distensae in skin phototypes IV-V with a TriPollar radiofrequency device" in the meeting of the European Academy of Dermatology and Venereology (EADV) Conference.