- "Striae" is also a general term referring to thin, narrow grooves or channels, or a thin line or band especially if several of them are parallel or close together.
Stretch marks or striae (singular stria), as they are called in dermatology, are a form of scarring on the skin with an off-color hue. They are caused by tearing of the dermis, which over time may diminish, but will not disappear completely.
Stretch marks are often the result of the rapid stretching of the skin associated with rapid growth or rapid weight changes. Stretch marks may also be influenced by hormonal changes associated with puberty, pregnancy, bodybuilding, hormone replacement therapy, etc.Medical terminology for these kinds of markings includes striae atrophicae, vergetures, stria distensae, striae cutis distensae, lineae atrophicae, linea albicante, or simply striae. Stretch marks formed during pregnancy, usually during the last trimester, and usually on the belly, but also commonly occurring on the breasts, thighs, hips, lower back and buttocks, are known as striae gravidarum.
Symptoms and signs
They first appear as reddish or purple lines, but tend to gradually fade to a lighter range. The affected areas appear empty and are soft to the touch. Stretch marks occur in the dermis, the resilient middle layer that helps the skin retain its shape. No stretch marks will form as long as there is support within the dermis. Stretching plays more of a role in where the marks occur and in what direction they run. Stretching alone is not the cause.
Stretch marks can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored. Most common places are the abdomen (especially near the navel), breasts, upper arms, underarms, back, thighs (both inner and outer), hips, and buttocks. They pose no health risk in and of themselves, and do not compromise the body's ability to function normally and repair itself.
A number of causes promote the appearance of stretchmarks: one study of 324 women just after giving birth demonstrated that low maternal age, high body mass index, weight gain over 15 kg (33 pounds) and higher neonatal birth weight were independently associated with the occurrence of striae. Teenagers are at highest risk of developing severe striae.
The glucocorticoid hormones responsible for the development of stretch marks affect the dermis by preventing the fibroblasts from forming collagen and elastin fibers, necessary to keep rapidly growing skin taut. This creates a lack of supportive material, as the skin is stretched and leads to dermal and epidermal tearing.
Skin subjected to more stretching force than it can handle will tear. Hormonal changes and genetics influence the skin's capacity to withstand stretching forces, as do diet and (possibly) exercise.
Striae gravidarum (pregnancy-related stretch marks) have been reported as occurring from 50% to 90% of pregnancies, partly as a result of the normal hormonal changes of pregnancy and partly due to stretching of skin fibers. A systematic review has not found evidence that the creams and oils that have been studied for preventing or reducing stretch marks in pregnancy are effective. The safety in pregnancy of one ingredient, Centella asiatica, has been questioned. Evidence on treatments for reducing the appearance of the scars after pregnancy is limited.
Various treatments are available for the purpose of improving the appearance of existing stretch marks, including , dermabrasion, and prescription retinoids. Topical tretinoin (prescription retinoid) is categorized by the FDA as a known teratogen (causing malformations in fetuses) in animals, without adequate human studies on safety in pregnancy. Some cream manufacturers claim the best results are achieved on recent stretch marks; however, few studies exist to support these claims.
A study in the journal Dermatologic Surgery showed that radiofrequency combined with 585-nm pulsed dye laser treatment gave "good and very good" subjective improvement in stretch marks in 33 of 37 patients, although further studies would be required to follow up on these results. In addition, the use of a pulsed dye laser was shown to increase pigmentation in darker skinned individuals with repeated treatments.
A surgical procedure for removing lower abdominal stretch marks is the tummy tuck, which removes the skin below the navel where stretch marks frequently occur.
A new modality, fractional laser resurfacing, offers a novel approach to treating striae. Using scattered pulses of light only a fraction of the scar is zapped by the laser over the course of several treatments. This creates microscopic wounds. The body responds to each treatment by producing new collagen and epithelium. In a 2007 clinical trial, 5-6 treatments resulted in striae improving by as much as 75 percent. A 2007 Brazilian clinical study showed that fractional laser resurfacing improved both texture and appearance of mature, white striae in skin types I-IV.
A recent study of new modality for the treatment of stretch marks published in the Journal of Dermatological Treatment was done on seventeen females with stretch marks that underwent six weekly treatments. Results showed that at one week after the final (sixth) treatment 38.2% and 11.8% of the patients were assessed to have 25-50% and 51-75% improvement in the appearance of their stretch marks, respectively. The long term effect of the treatment was confirmed during the 6 weeks follow up which showed that a higher percentage of the patients were rated to have improvement of their stretch marks, including 26.5% and 5.9% showing 51-75% and >75% improvement, respectively. None of the participants was rated as having no improvement in their clinical appearance of stretch marks. Patient satisfaction was also measured and 65% of patients reported that they were very satisfied with the treatment, 23% were satisfied and 12% were slightly satisfied.